A116831 Number of permutations of length n which avoid the patterns 3124, 3241, 4321.

1, 2, 6, 21, 74, 247, 769, 2247, 6238, 16649, 43132, 109257, 272073, 668704, 1626916, 3926643, 9416939, 22468173, 53383884, 126404204, 298455204, 703023125, 1652724170, 3878899500, 9090904341, 21280894049, 49766276975, 116280945813

Offset

1,2

Links

Table of n, a(n) for n=1..28.

D. Callan, T. Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 [math.CO] (2017), Table 2 No 117.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (10,-43,105,-162,166,-115,53,-15,2).

Formula

G.f.: A(x) = -{x(x^8-9x^7+31x^6-62x^5+74x^4-58x^3+29x^2-8x+1)}/{(x-1)^5(2x-1)(x^3-2x^2+3x-1)}

Crossrefs

Sequence in context: A116771 A294765 A116745 * A294698 A294766 A116752

Adjacent sequences: A116828 A116829 A116830 * A116832 A116833 A116834

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved