A294822 Number of permutations of [n] avoiding {1243, 1324, 2431}.

1, 1, 2, 6, 21, 77, 283, 1032, 3740, 13522, 48930, 177564, 646908, 2367121, 8699706, 32108614, 118975273, 442467434, 1651076429, 6180073782, 23197995681, 87304824502, 329357941951, 1245262325246, 4717865597299, 17908489016748, 68099538024617, 259388123347450, 989533568712759

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 210.

Maple

C := (1-sqrt(1-4*x))/2/x ;
(1 -6*x +13*x^2 -11*x^3 +4*x^4)/(x^2*(1 -x)^2)*C -(1 -6*x +12*x^2 -8*x^3 +2*x^4)/(x^2*(1 -x)*(1 -2*x)) ;
taylor(%, x=0, 40) ;
gfun[seriestolist](%) ;

Crossrefs

Sequence in context: A131792 A144904 A151287 * A294823 A294824 A294825

Adjacent sequences: A294819 A294820 A294821 * A294823 A294824 A294825

Keyword

nonn,easy

Author

R. J. Mathar, Nov 09 2017

Status

approved