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URL: https://oeis.org/A116737

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A116737

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

0

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

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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