A294825 Number of permutations of [n] avoiding {2431, 1324, 1342}.

1, 1, 2, 6, 21, 77, 285, 1054, 3889, 14330, 52800, 194748, 719602, 2664989, 9894443, 36831886, 137465657, 514370974, 1929432068, 7254441076, 27336758102, 103229845714, 390594944522, 1480679644876, 5622915464986, 21388666960212, 81486623660720, 310907347188280, 1187905972634884

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 213.

Maple

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

Crossrefs

Sequence in context: A294822 A294823 A294824 * A101265 A101879 A242622

Adjacent sequences: A294822 A294823 A294824 * A294826 A294827 A294828

Keyword

nonn,easy

Author

R. J. Mathar, Nov 09 2017

Status

approved