A116738 Number of permutations of length n which avoid the patterns 3214, 4123, 4132.

1, 2, 6, 21, 74, 260, 913, 3206, 11258, 39533, 138822, 487480, 1711809, 6011098, 21108254, 74122629, 260285106, 914003420, 3209566097, 11270542654, 39577041842, 138976648157, 488023051598, 1713715951920, 6017794352641

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 142.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (4,-2,1).

Formula

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

Crossrefs

Sequence in context: A116817 A116764 A294769 * A360151 A150186 A150187

Adjacent sequences: A116735 A116736 A116737 * A116739 A116740 A116741

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved