A116789 Number of permutations of length n which avoid the patterns 1234, 2431, 3241.

1, 2, 6, 21, 73, 231, 650, 1668, 3987, 9030, 19628, 41333, 84915, 171087, 339408, 665004, 1289881, 2481422, 4741442, 9009137, 17038193, 32096591, 60263770, 112832696, 210754191, 392853778, 731013500, 1358206773, 2520242339

Offset

1,2

Links

Table of n, a(n) for n=1..29.

D. Callan, T. Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 (2017), Table 2 No 65.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (5,-8,3,2,1,-2,-1,1).

Formula

G.f.: A(x) = -{(4x^7+4x^6+11x^5+8x^4+4x^3+4x^2-3x+1)x}/{(x^2-x+1)(x-1)^3(x^3+x^2+x-1)}

Crossrefs

Sequence in context: A116803 A116829 A116824 * A116783 A116739 A116770

Adjacent sequences: A116786 A116787 A116788 * A116790 A116791 A116792

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved