Av(1324, 1342, 3412, 4123)
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Generating Function
\(\displaystyle -\frac{8 x^{5}-21 x^{4}+28 x^{3}-20 x^{2}+7 x -1}{\left(2 x -1\right)^{2} \left(-1+x \right)^{4}}\)
Counting Sequence
1, 1, 2, 6, 20, 63, 182, 488, 1236, 3001, 7062, 16234, 36660, 81651, 179878, ...
Implicit Equation for the Generating Function
\(\displaystyle \left(2 x -1\right)^{2} \left(-1+x \right)^{4} F \! \left(x \right)+8 x^{5}-21 x^{4}+28 x^{3}-20 x^{2}+7 x -1 = 0\)
Recurrence
\(\displaystyle a \! \left(0\right) = 1\)
\(\displaystyle a \! \left(1\right) = 1\)
\(\displaystyle a \! \left(2\right) = 2\)
\(\displaystyle a \! \left(3\right) = 6\)
\(\displaystyle a \! \left(4\right) = 20\)
\(\displaystyle a \! \left(5\right) = 63\)
\(\displaystyle a \! \left(n +2\right) = -\frac{n^{3}}{6}+\frac{3 n^{2}}{2}-4 a \! \left(n \right)+4 a \! \left(n +1\right)-\frac{4 n}{3}+2, \quad n \geq 6\)
Explicit Closed Form
\(\displaystyle 4+\frac{n^{2}}{2}+\frac{2 n}{3}-\frac{n^{3}}{6}+2^{n} n -3 \,2^{n}\)

This specification was found using the strategy pack "Point Placements" and has 173 rules.

Found on July 23, 2021.

Finding the specification took 12 seconds.

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\(\begin{align*} F_{0}\! \left(x \right) &= F_{1}\! \left(x \right)+F_{2}\! \left(x \right)\\ F_{1}\! \left(x \right) &= 1\\ F_{2}\! \left(x \right) &= F_{3}\! \left(x \right)\\ F_{3}\! \left(x \right) &= F_{4}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{4}\! \left(x \right) &= F_{0}\! \left(x \right)+F_{5}\! \left(x \right)\\ F_{5}\! \left(x \right) &= F_{47}\! \left(x \right)+F_{6}\! \left(x \right)\\ F_{6}\! \left(x \right) &= F_{7}\! \left(x \right)\\ F_{7}\! \left(x \right) &= F_{8}\! \left(x \right) F_{9}\! \left(x \right)\\ F_{8}\! \left(x \right) &= x\\ F_{9}\! \left(x \right) &= F_{10}\! \left(x \right)+F_{13}\! \left(x \right)\\ F_{10}\! \left(x \right) &= F_{1}\! \left(x \right)+F_{11}\! \left(x \right)\\ F_{11}\! \left(x \right) &= F_{12}\! \left(x \right)\\ F_{12}\! \left(x \right) &= F_{10}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{13}\! \left(x \right) &= F_{14}\! \left(x \right)+F_{29}\! \left(x \right)\\ F_{14}\! \left(x \right) &= F_{15}\! \left(x \right)\\ F_{15}\! \left(x \right) &= F_{16}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{16}\! \left(x \right) &= F_{17}\! \left(x \right)+F_{18}\! \left(x \right)\\ F_{17}\! \left(x \right) &= F_{1}\! \left(x \right)+F_{8}\! \left(x \right)\\ F_{18}\! \left(x \right) &= F_{14}\! \left(x \right)+F_{19}\! \left(x \right)\\ F_{19}\! \left(x \right) &= F_{20}\! \left(x \right)+F_{21}\! \left(x \right)+F_{25}\! \left(x \right)\\ F_{20}\! \left(x \right) &= 0\\ F_{21}\! \left(x \right) &= F_{22}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{22}\! \left(x \right) &= F_{23}\! \left(x \right)+F_{24}\! \left(x \right)\\ F_{23}\! \left(x \right) &= F_{8}\! \left(x \right)\\ F_{24}\! \left(x \right) &= F_{19}\! \left(x \right)\\ F_{25}\! \left(x \right) &= F_{26}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{26}\! \left(x \right) &= F_{27}\! \left(x \right)\\ F_{27}\! \left(x \right) &= F_{28}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{28}\! \left(x \right) &= F_{1}\! \left(x \right)+F_{26}\! \left(x \right)\\ F_{29}\! \left(x \right) &= F_{20}\! \left(x \right)+F_{30}\! \left(x \right)+F_{45}\! \left(x \right)\\ F_{30}\! \left(x \right) &= F_{31}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{31}\! \left(x \right) &= F_{32}\! \left(x \right)+F_{35}\! \left(x \right)\\ F_{32}\! \left(x \right) &= F_{11}\! \left(x \right)+F_{33}\! \left(x \right)\\ F_{33}\! \left(x \right) &= F_{34}\! \left(x \right)\\ F_{34}\! \left(x \right) &= F_{11}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{35}\! \left(x \right) &= F_{29}\! \left(x \right)+F_{36}\! \left(x \right)\\ F_{36}\! \left(x \right) &= 2 F_{20}\! \left(x \right)+F_{37}\! \left(x \right)+F_{41}\! \left(x \right)\\ F_{37}\! \left(x \right) &= F_{38}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{38}\! \left(x \right) &= F_{39}\! \left(x \right)+F_{40}\! \left(x \right)\\ F_{39}\! \left(x \right) &= F_{33}\! \left(x \right)\\ F_{40}\! \left(x \right) &= F_{36}\! \left(x \right)\\ F_{41}\! \left(x \right) &= F_{42}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{42}\! \left(x \right) &= F_{20}\! \left(x \right)+F_{43}\! \left(x \right)+F_{45}\! \left(x \right)\\ F_{43}\! \left(x \right) &= F_{44}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{44}\! \left(x \right) &= F_{11}\! \left(x \right)+F_{42}\! \left(x \right)\\ F_{45}\! \left(x \right) &= F_{46}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{46}\! \left(x \right) &= F_{26}\! \left(x \right)+F_{42}\! \left(x \right)\\ F_{47}\! \left(x \right) &= F_{48}\! \left(x \right)\\ F_{48}\! \left(x \right) &= F_{49}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{49}\! \left(x \right) &= F_{5}\! \left(x \right)+F_{50}\! \left(x \right)\\ F_{50}\! \left(x \right) &= F_{167}\! \left(x \right)+F_{51}\! \left(x \right)\\ F_{51}\! \left(x \right) &= F_{52}\! \left(x \right)\\ F_{52}\! \left(x \right) &= F_{28}\! \left(x \right) F_{53}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{53}\! \left(x \right) &= F_{106}\! \left(x \right)+F_{54}\! \left(x \right)\\ F_{54}\! \left(x \right) &= F_{28}\! \left(x \right)+F_{55}\! \left(x \right)\\ F_{55}\! \left(x \right) &= F_{56}\! \left(x \right)+F_{6}\! \left(x \right)\\ F_{56}\! \left(x \right) &= F_{20}\! \left(x \right)+F_{57}\! \left(x \right)+F_{81}\! \left(x \right)\\ F_{57}\! \left(x \right) &= F_{58}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{58}\! \left(x \right) &= F_{59}\! \left(x \right)+F_{66}\! \left(x \right)\\ F_{59}\! \left(x \right) &= F_{26}\! \left(x \right)+F_{60}\! \left(x \right)\\ F_{60}\! \left(x \right) &= F_{20}\! \left(x \right)+F_{61}\! \left(x \right)+F_{62}\! \left(x \right)\\ F_{61}\! \left(x \right) &= F_{59}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{62}\! \left(x \right) &= F_{63}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{63}\! \left(x \right) &= F_{64}\! \left(x \right)+F_{8}\! \left(x \right)\\ F_{64}\! \left(x \right) &= F_{20}\! \left(x \right)+F_{62}\! \left(x \right)+F_{65}\! \left(x \right)\\ F_{65}\! \left(x \right) &= F_{26}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{66}\! \left(x \right) &= F_{67}\! \left(x \right)+F_{87}\! \left(x \right)\\ F_{67}\! \left(x \right) &= F_{20}\! \left(x \right)+F_{68}\! \left(x \right)+F_{81}\! \left(x \right)\\ F_{68}\! \left(x \right) &= F_{69}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{69}\! \left(x \right) &= F_{70}\! \left(x \right)+F_{71}\! \left(x \right)\\ F_{70}\! \left(x \right) &= F_{26}\! \left(x \right)+F_{64}\! \left(x \right)\\ F_{71}\! \left(x \right) &= F_{67}\! \left(x \right)+F_{72}\! \left(x \right)\\ F_{72}\! \left(x \right) &= F_{20}\! \left(x \right)+F_{73}\! \left(x \right)+F_{77}\! \left(x \right)+F_{83}\! \left(x \right)\\ F_{73}\! \left(x \right) &= F_{74}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{74}\! \left(x \right) &= F_{75}\! \left(x \right)+F_{76}\! \left(x \right)\\ F_{75}\! \left(x \right) &= F_{64}\! \left(x \right)\\ F_{76}\! \left(x \right) &= F_{72}\! \left(x \right)\\ F_{77}\! \left(x \right) &= F_{78}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{78}\! \left(x \right) &= F_{20}\! \left(x \right)+F_{79}\! \left(x \right)+F_{81}\! \left(x \right)\\ F_{79}\! \left(x \right) &= F_{8}\! \left(x \right) F_{80}\! \left(x \right)\\ F_{80}\! \left(x \right) &= F_{26}\! \left(x \right)+F_{78}\! \left(x \right)\\ F_{81}\! \left(x \right) &= F_{8}\! \left(x \right) F_{82}\! \left(x \right)\\ F_{82}\! \left(x \right) &= F_{26}\! \left(x \right)+F_{78}\! \left(x \right)\\ F_{83}\! \left(x \right) &= F_{8}\! \left(x \right) F_{84}\! \left(x \right)\\ F_{84}\! \left(x \right) &= F_{85}\! \left(x \right)+F_{86}\! \left(x \right)\\ F_{85}\! \left(x \right) &= F_{25}\! \left(x \right)\\ F_{86}\! \left(x \right) &= 2 F_{20}\! \left(x \right)+F_{77}\! \left(x \right)+F_{83}\! \left(x \right)\\ F_{87}\! \left(x \right) &= F_{103}\! \left(x \right)+F_{20}\! \left(x \right)+F_{83}\! \left(x \right)+F_{88}\! \left(x \right)\\ F_{88}\! \left(x \right) &= F_{8}\! \left(x \right) F_{89}\! \left(x \right)\\ F_{89}\! \left(x \right) &= F_{90}\! \left(x \right)+F_{93}\! \left(x \right)\\ F_{90}\! \left(x \right) &= F_{60}\! \left(x \right)+F_{91}\! \left(x \right)\\ F_{91}\! \left(x \right) &= F_{92}\! \left(x \right)\\ F_{92}\! \left(x \right) &= F_{60}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{93}\! \left(x \right) &= F_{87}\! \left(x \right)+F_{94}\! \left(x \right)\\ F_{94}\! \left(x \right) &= 2 F_{20}\! \left(x \right)+F_{105}\! \left(x \right)+F_{95}\! \left(x \right)+F_{99}\! \left(x \right)\\ F_{95}\! \left(x \right) &= F_{8}\! \left(x \right) F_{96}\! \left(x \right)\\ F_{96}\! \left(x \right) &= F_{97}\! \left(x \right)+F_{98}\! \left(x \right)\\ F_{97}\! \left(x \right) &= F_{91}\! \left(x \right)\\ F_{98}\! \left(x \right) &= F_{94}\! \left(x \right)\\ F_{99}\! \left(x \right) &= F_{100}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{100}\! \left(x \right) &= F_{101}\! \left(x \right)+F_{103}\! \left(x \right)+F_{20}\! \left(x \right)+F_{83}\! \left(x \right)\\ F_{101}\! \left(x \right) &= F_{102}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{102}\! \left(x \right) &= F_{100}\! \left(x \right)+F_{60}\! \left(x \right)\\ F_{103}\! \left(x \right) &= F_{104}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{104}\! \left(x \right) &= F_{100}\! \left(x \right)+F_{78}\! \left(x \right)\\ F_{105}\! \left(x \right) &= 0\\ F_{106}\! \left(x \right) &= F_{107}\! \left(x \right)+F_{148}\! \left(x \right)\\ F_{107}\! \left(x \right) &= F_{108}\! \left(x \right)+F_{6}\! \left(x \right)\\ F_{108}\! \left(x \right) &= F_{109}\! \left(x \right)\\ F_{109}\! \left(x \right) &= F_{110}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{110}\! \left(x \right) &= F_{111}\! \left(x \right)+F_{114}\! \left(x \right)\\ F_{111}\! \left(x \right) &= F_{112}\! \left(x \right)+F_{26}\! \left(x \right)\\ F_{112}\! \left(x \right) &= F_{113}\! \left(x \right)\\ F_{113}\! \left(x \right) &= F_{111}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{114}\! \left(x \right) &= F_{115}\! \left(x \right)+F_{130}\! \left(x \right)\\ F_{115}\! \left(x \right) &= F_{116}\! \left(x \right)\\ F_{116}\! \left(x \right) &= F_{117}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{117}\! \left(x \right) &= F_{118}\! \left(x \right)+F_{120}\! \left(x \right)\\ F_{118}\! \left(x \right) &= F_{119}\! \left(x \right)+F_{26}\! \left(x \right)\\ F_{119}\! \left(x \right) &= F_{65}\! \left(x \right)\\ F_{120}\! \left(x \right) &= F_{115}\! \left(x \right)+F_{121}\! \left(x \right)\\ F_{121}\! \left(x \right) &= 2 F_{20}\! \left(x \right)+F_{122}\! \left(x \right)+F_{126}\! \left(x \right)\\ F_{122}\! \left(x \right) &= F_{123}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{123}\! \left(x \right) &= F_{124}\! \left(x \right)+F_{125}\! \left(x \right)\\ F_{124}\! \left(x \right) &= F_{119}\! \left(x \right)\\ F_{125}\! \left(x \right) &= F_{121}\! \left(x \right)\\ F_{126}\! \left(x \right) &= F_{127}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{127}\! \left(x \right) &= F_{128}\! \left(x \right)\\ F_{128}\! \left(x \right) &= F_{129}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{129}\! \left(x \right) &= F_{127}\! \left(x \right)+F_{26}\! \left(x \right)\\ F_{130}\! \left(x \right) &= 2 F_{20}\! \left(x \right)+F_{131}\! \left(x \right)+F_{146}\! \left(x \right)\\ F_{131}\! \left(x \right) &= F_{132}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{132}\! \left(x \right) &= F_{133}\! \left(x \right)+F_{136}\! \left(x \right)\\ F_{133}\! \left(x \right) &= F_{112}\! \left(x \right)+F_{134}\! \left(x \right)\\ F_{134}\! \left(x \right) &= F_{135}\! \left(x \right)\\ F_{135}\! \left(x \right) &= F_{112}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{136}\! \left(x \right) &= F_{130}\! \left(x \right)+F_{137}\! \left(x \right)\\ F_{137}\! \left(x \right) &= 3 F_{20}\! \left(x \right)+F_{138}\! \left(x \right)+F_{142}\! \left(x \right)\\ F_{138}\! \left(x \right) &= F_{139}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{139}\! \left(x \right) &= F_{140}\! \left(x \right)+F_{141}\! \left(x \right)\\ F_{140}\! \left(x \right) &= F_{134}\! \left(x \right)\\ F_{141}\! \left(x \right) &= F_{137}\! \left(x \right)\\ F_{142}\! \left(x \right) &= F_{143}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{143}\! \left(x \right) &= 2 F_{20}\! \left(x \right)+F_{144}\! \left(x \right)+F_{146}\! \left(x \right)\\ F_{144}\! \left(x \right) &= F_{145}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{145}\! \left(x \right) &= F_{112}\! \left(x \right)+F_{143}\! \left(x \right)\\ F_{146}\! \left(x \right) &= F_{147}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{147}\! \left(x \right) &= F_{127}\! \left(x \right)+F_{143}\! \left(x \right)\\ F_{148}\! \left(x \right) &= F_{149}\! \left(x \right)+F_{158}\! \left(x \right)\\ F_{149}\! \left(x \right) &= F_{150}\! \left(x \right)\\ F_{150}\! \left(x \right) &= F_{151}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{151}\! \left(x \right) &= F_{152}\! \left(x \right)+F_{153}\! \left(x \right)\\ F_{152}\! \left(x \right) &= F_{26}\! \left(x \right)\\ F_{153}\! \left(x \right) &= F_{154}\! \left(x \right)\\ F_{154}\! \left(x \right) &= F_{155}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{155}\! \left(x \right) &= F_{156}\! \left(x \right)+F_{157}\! \left(x \right)\\ F_{156}\! \left(x \right) &= F_{26}\! \left(x \right)\\ F_{157}\! \left(x \right) &= F_{154}\! \left(x \right)\\ F_{158}\! \left(x \right) &= F_{159}\! \left(x \right)\\ F_{159}\! \left(x \right) &= F_{160}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{160}\! \left(x \right) &= F_{161}\! \left(x \right)+F_{162}\! \left(x \right)\\ F_{161}\! \left(x \right) &= F_{127}\! \left(x \right)\\ F_{162}\! \left(x \right) &= F_{163}\! \left(x \right)\\ F_{163}\! \left(x \right) &= F_{164}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{164}\! \left(x \right) &= F_{165}\! \left(x \right)+F_{166}\! \left(x \right)\\ F_{165}\! \left(x \right) &= F_{127}\! \left(x \right)\\ F_{166}\! \left(x \right) &= F_{163}\! \left(x \right)\\ F_{167}\! \left(x \right) &= F_{168}\! \left(x \right) F_{26}\! \left(x \right)\\ F_{168}\! \left(x \right) &= F_{169}\! \left(x \right)+F_{26}\! \left(x \right)\\ F_{169}\! \left(x \right) &= F_{170}\! \left(x \right)+F_{171}\! \left(x \right)+F_{20}\! \left(x \right)\\ F_{170}\! \left(x \right) &= F_{168}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{171}\! \left(x \right) &= F_{172}\! \left(x \right) F_{8}\! \left(x \right)\\ F_{172}\! \left(x \right) &= F_{169}\! \left(x \right)+F_{26}\! \left(x \right)\\ \end{align*}\)