cp's OEIS Frontend

A317287 Number of permutations of [n] with exactly seven increasing runs of even length.

%I A317287 #6 Jul 25 2018 17:13:22
%S A317287 199360981,11190963430,378291607803,11014069796526,305943708449074,
%T A317287 8211684416287224,215906484804391566,5654455021954104792,
%U A317287 148657867362265421769,3937297418900898841450,105451222548147683308147,2864250745636538809593802,79027581972356621300952774
%N A317287 Number of permutations of [n] with exactly seven increasing runs of even length.
%H A317287 Alois P. Heinz, <a href="/A317287/b317287.txt">Table of n, a(n) for n = 14..469</a>
%p A317287 b:= proc(u, o, t) option remember; series(`if`(u+o=0, x^t,
%p A317287       add(b(u+j-1, o-j, irem(t+1, 2)), j=1..o)+
%p A317287       add(b(u-j, o+j-1, 0)*x^t, j=1..u)), x, 8)
%p A317287     end:
%p A317287 a:= n-> coeff(b(n, 0$2), x, 7):
%p A317287 seq(a(n), n=14..30);
%Y A317287 Column k=7 of A097592.
%K A317287 nonn
%O A317287 14,1
%A A317287 _Alois P. Heinz_, Jul 25 2018