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A116813

Number of permutations of length n which avoid the patterns 1234, 2431, 4213.

1, 2, 6, 21, 70, 192, 441, 929, 1870, 3670, 7097, 13600, 25907, 49142, 92911, 175190, 329563, 618681, 1159262, 2168484, 4050003, 7553315, 14068790, 26173531, 48640712, 90304947, 167508064, 310461529, 574989748, 1064197426

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..30.

D. Callan, T. Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 (2017), Table 2 No 8 (typo: factor 2 in the 2nd denominator missing in v2).

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (6,-12,6,7,-4,-5,0,4,0,-1)

FORMULA

G.f.: x(6x^13 +8x^12 -23x^11 -49x^10 -15x^9 +56x^8 +54x^7 -26x^6 -22x^5 -3x^4 +3x^3 +6x^2 -4x+1)/((x^2-1+x)^2 (x^3+x^2+x-1) (x-1)^3).

CROSSREFS

Sequence in context: A294709 A116774 A116756 * A116765 A116815 A116804

Adjacent sequences: A116810 A116811 A116812 * A116814 A116815 A116816

KEYWORD

nonn,easy

AUTHOR

Lara Pudwell, Feb 26 2006

STATUS

approved

URL: https://oeis.org/A116813

⇱ A116813 - OEIS