A116781 Number of permutations of length n which avoid the patterns 1234, 1243, 3214.

1, 2, 6, 21, 73, 250, 861, 2967, 10220, 35203, 121263, 417710, 1438865, 4956391, 17073052, 58810751, 202582667, 697827126, 2403772765, 8280164651, 28522299468, 98249443251, 338435304271, 1165792409470, 4015751089881

Offset

1,2

Links

Table of n, a(n) for n=1..25.

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 113.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (3,1,2,0,-2)

Formula

G.f.: A(x) = -{x(x^3+x^2+x-1)}/{2x^5-2x^3-x^2-3x+1}

Crossrefs

Sequence in context: A116828 A294764 A116837 * A047106 A360152 A148487

Adjacent sequences: A116778 A116779 A116780 * A116782 A116783 A116784

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved