A098995 Number of permutations of [n] with exactly 4 descents which avoid the pattern 1324.

0, 0, 0, 0, 1, 57, 812, 6524, 37309, 169298, 648216, 2176923, 6582869, 18262399, 47129249, 114344261, 262987603, 577216181, 1215552037, 2467076907, 4843870146, 9229556242, 17113017451, 30949065535, 54705281270, 94677736245, 160689668475, 267828562140, 438931138500

Offset

1,6

Links

T. D. Noe, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (17,-136,680,-2380,6188,-12376,19448,-24310,24310,-19448,12376,-6188,2380,-680,136,-17,1).

Formula

G.f.: x^5*(1 + 40*x - 21*x^2 - 208*x^3 + 453*x^4 - 379*x^5 + 74*x^6 + 107*x^7 - 92*x^8 + 30*x^9 - 4*x^10) / (1 - x)^17.

Prog

(PARI) concat(vector(4), Vec(x^5*(1 + 40*x - 21*x^2 - 208*x^3 + 453*x^4 - 379*x^5 + 74*x^6 + 107*x^7 - 92*x^8 + 30*x^9 - 4*x^10) / (1 - x)^17 + O(x^30))) \\ Colin Barker, Nov 03 2017

Crossrefs

Cf. A061552, A000292.

Sequence in context: A084220 A060891 A241967 * A210156 A210149 A254783

Adjacent sequences: A098992 A098993 A098994 * A098996 A098997 A098998

Keyword

easy,nonn

Author

Mike Zabrocki, Nov 05 2004

Status

approved