A294815 Number of permutations of [n] avoiding {2143, 4132, 1324}.

1, 1, 2, 6, 21, 75, 265, 927, 3229, 11253, 39355, 138362, 489440, 1742576, 6244395, 22516585, 81673947, 297894234, 1092086024, 4022418903, 14879231036, 55255415912, 205931156743, 769994355746, 2887687533958, 10859294097589, 40939724979676, 154701255400490, 585829636549849, 2222842322625552

Offset

0,3

Links

Table of n, a(n) for n=0..29.

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 172.

Maple

C := (1-sqrt(1-4*x))/2/x ;
((2 -10*x +16*x^2 -8*x^3 +x^4)*C -1 +4*x -5*x^2 +x^3)/((1 -x)^2*(1 -3*x + x^2)) ;
taylor(%, x=0, 40) ;
gfun[seriestolist](%) ;

Crossrefs

Sequence in context: A116736 A116820 A369626 * A116751 A116823 A289597

Adjacent sequences: A294812 A294813 A294814 * A294816 A294817 A294818

Keyword

nonn,easy

Author

R. J. Mathar, Nov 09 2017

Status

approved