A116788 Number of permutations of length n which avoid the patterns 1234, 3142, 4132.

1, 2, 6, 21, 73, 240, 746, 2217, 6371, 17864, 49202, 133759, 360175, 963044, 2561604, 6787167, 17930815, 47267250, 124395032, 326966211, 858600521, 2253029402, 5908876016, 15490375561, 40595804773, 106364147270, 278630854386

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 [math.CO] (2017), Table 2 No 89.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (8,-25,39,-32,13,-2)

Formula

G.f.: A(x) = -{(2x^5-9x^4+16x^3-15x^2+6x-1)x}/{(2x-1)(x-1)^3(x^2-3x+1)}

Crossrefs

Sequence in context: A294694 A116740 A294802 * A294695 A116778 A116787

Adjacent sequences: A116785 A116786 A116787 * A116789 A116790 A116791

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved