A116737 Number of permutations of length n which avoid the patterns 3412, 4123, 4321.

1, 2, 6, 21, 72, 246, 845, 2901, 9955, 34165, 117254, 402409, 1381046, 4739681, 16266344, 55825262, 191589456, 657525254, 2256593172, 7744512803, 26578773396, 91216996231, 313052083987, 1074378803719, 3687213319833

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 (2017), Table 2 No 57.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

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

Formula

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

Crossrefs

Sequence in context: A116836 A116796 A116779 * A360153 A294759 A294760

Adjacent sequences: A116734 A116735 A116736 * A116738 A116739 A116740

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved