A116785 Number of permutations of length n which avoid the patterns 2143, 2341, 4213.

1, 2, 6, 21, 71, 222, 652, 1838, 5053, 13682, 36697, 97814, 259585, 686709, 1812257, 4773804, 12557136, 32994311, 86620279, 227256969, 595933506, 1562111927, 4093542416, 10724799901, 28093431826, 73580651302, 192698841652

Offset

1,2

Links

Table of n, a(n) for n=1..27.

D. Callan, T. Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 (2017), Table 2 No 36.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (10,-42,97,-135,116,-60,17,-2).

Formula

G.f.: A(x) = -{(3x^7-15x^6+34x^5-54x^4+52x^3-28x^2+8x-1)x}/{(2x-1)(x^2-3x+1)(x-1)^5}

Crossrefs

Sequence in context: A116761 A116807 A294702 * A116801 A148486 A294753

Adjacent sequences: A116782 A116783 A116784 * A116786 A116787 A116788

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved