A116764 - OEIS

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A116764

Number of permutations of length n which avoid the patterns 1423, 2134, 3214.

1, 2, 6, 21, 74, 257, 886, 3050, 10505, 36206, 124833, 430474, 1484526, 5119597, 17655746, 60888801, 209985534, 724171922, 2497434881, 8612847430, 29702935745, 102435859346, 353268294998, 1218308608389, 4201554149626

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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 [math.CO] (2017), Table 2 No 140.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (7,-17,19,-9).

FORMULA

G.f.: A(x) = -{(2x-1)(3x^2-3x+1)x}/{9x^4-19x^3+17x^2-7x+1}

CROSSREFS

Sequence in context: A116805 A116790 A116817 * A294769 A116738 A360151

Adjacent sequences: A116761 A116762 A116763 * A116765 A116766 A116767

KEYWORD

nonn,easy

AUTHOR

Lara Pudwell, Feb 26 2006

STATUS

approved