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

2404879675441, 208031951035452, 10539887638301128, 438391470941407244, 16755405367563104497, 607314204208297961718, 21247637795898419646167, 729013114914519439841722, 24775048055015061709737839, 838857400014414535124226202, 28428368151331776174951956983

Offset: 18

Author

Alois P. Heinz, Jul 25 2018

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 18..468

Crossrefs

Column k=9 of A097592.

Programs

Maple

b:= proc(u, o, t) option remember; series(`if`(u+o=0, x^t,
      add(b(u+j-1, o-j, irem(t+1, 2)), j=1..o)+
      add(b(u-j, o+j-1, 0)*x^t, j=1..u)), x, 10)
    end:
a:= n-> coeff(b(n, 0$2), x, 9):
seq(a(n), n=18..30);