A116821 Number of permutations of length n which avoid the patterns 1234, 1324, 1432.

1, 2, 6, 21, 76, 278, 1019, 3734, 13678, 50100, 183514, 672230, 2462490, 9020556, 33043996, 121046420, 443416116, 1624318192, 5950189652, 21796689568, 79845470136, 292489332488, 1071444754512, 3924908494984, 14377695776152

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 205.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (8,-24,38,-34,14,-2).

Formula

G.f.: A(x) = -{x(-1+6x-10x^4+17x^3+x^6-14x^2)}/{34x^4-38x^3+24x^2-14x^5-8x+1+2x^6}

Mathematica

LinearRecurrence[{8, -24, 38, -34, 14, -2}, {1, 2, 6, 21, 76, 278, 1019}, 30] (* Harvey P. Dale, Apr 20 2024 *)

Crossrefs

Sequence in context: A108146 A116798 A279560 * A116772 A131792 A144904

Adjacent sequences: A116818 A116819 A116820 * A116822 A116823 A116824

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved