cp's OEIS Frontend

A317289 Number of permutations of [n] with exactly nine increasing runs of even length.

%I A317289 #4 Jul 25 2018 16:38:37
%S A317289 2404879675441,208031951035452,10539887638301128,438391470941407244,
%T A317289 16755405367563104497,607314204208297961718,21247637795898419646167,
%U A317289 729013114914519439841722,24775048055015061709737839,838857400014414535124226202,28428368151331776174951956983
%N A317289 Number of permutations of [n] with exactly nine increasing runs of even length.
%H A317289 Alois P. Heinz, <a href="/A317289/b317289.txt">Table of n, a(n) for n = 18..468</a>
%p A317289 b:= proc(u, o, t) option remember; series(`if`(u+o=0, x^t,
%p A317289       add(b(u+j-1, o-j, irem(t+1, 2)), j=1..o)+
%p A317289       add(b(u-j, o+j-1, 0)*x^t, j=1..u)), x, 10)
%p A317289     end:
%p A317289 a:= n-> coeff(b(n, 0$2), x, 9):
%p A317289 seq(a(n), n=18..30);
%Y A317289 Column k=9 of A097592.
%K A317289 nonn
%O A317289 18,1
%A A317289 _Alois P. Heinz_, Jul 25 2018