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A116840

Number of permutations of length n which avoid the patterns 1234, 1243, 2431.

1, 2, 6, 21, 75, 256, 826, 2535, 7474, 21370, 59718, 164082, 445266, 1197326, 3198035, 8499466, 22505676, 59427975, 156598649, 412008060, 1082704623, 2842662437, 7458393801, 19558738331, 51270256195, 134356895501

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..26.

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 146.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (10,-42,97,-135,116,-60,17,-2).

FORMULA

G.f.: (x^8 -6x^7 +17x^6 -40x^5 +58x^4 -52x^3 +28x^2 -8x+1)*x/((2x-1) (x^2-3x+1)(x-1)^5)

CROSSREFS

Sequence in context: A116818 A294770 A116763 * A116841 A116814 A294806

Adjacent sequences: A116837 A116838 A116839 * A116841 A116842 A116843

KEYWORD

nonn,easy

AUTHOR

Lara Pudwell, Feb 26 2006

STATUS

approved

URL: https://oeis.org/A116840

⇱ A116840 - OEIS