A116802 Number of permutations of length n which avoid the patterns 1342, 3421, 4213.

1, 2, 6, 21, 73, 244, 787, 2468, 7570, 22809, 67727, 198664, 576775, 1659914, 4741254, 13454541, 37964341, 106590076, 297951451, 829614896, 2301930586, 6367200417, 17562228251, 48317182096, 132621950863, 363253065494

Offset

1,2

Links

Table of n, a(n) for n=1..26.

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 105.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (10,-40,82,-92,56,-17,2).

Formula

G.f.: A(x) = -{x(2x^6-10x^5+31x^4-41x^3+26x^2-8x+1)}/{(2x-1)(x-1)^2(x^2-3x+1)^2}

Crossrefs

Sequence in context: A294696 A116784 A226431 * A294697 A116826 A116760

Adjacent sequences: A116799 A116800 A116801 * A116803 A116804 A116805

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved