A294819 - OEIS

A294819

Number of permutations of [n] avoiding {1324, 2431, 3142}.

1, 1, 2, 6, 21, 76, 275, 989, 3539, 12631, 45066, 161021, 576887, 2074166, 7488003, 27150233, 98878251, 361680595, 1328574654, 4900021037, 18141052047, 67402330234, 251263851255, 939561899651, 3523414637736, 13248113693491, 49935804727105, 188651583360524, 714214447347319

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OFFSET

0,3

LINKS

Table of n, a(n) for n=0..28.

D. Callan, T. Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 [math.CO] (2017), Table 1 No 193.

FORMULA

D-finite with recurrence 2*(n+1)*a(n) +(-19*n+3)*a(n-1) +2*(31*n-39)*a(n-2) +2*(-40*n+93)*a(n-3) +(33*n-107)*a(n-4) +2*(-2*n+9)*a(n-5)=0. - R. J. Mathar, Jan 18 2021

MAPLE

C := (1-sqrt(1-4*x))/2/x ;

(x -1 +(x^2 -5*x +2)*C)/(1 -3*x +x^2) ;

taylor(%, x=0, 40) ;

gfun[seriestolist](%) ;

CROSSREFS

Sequence in context: A294818 A116809 A116819 * A294820 A116782 A112091

Adjacent sequences: A294816 A294817 A294818 * A294820 A294821 A294822

KEYWORD

nonn,easy

AUTHOR

R. J. Mathar, Nov 09 2017

STATUS

approved