A317285 Number of permutations of [n] with exactly five increasing runs of even length.

50521, 1629248, 32918922, 617859020, 11668739836, 217316513198, 4043244094251, 76688877688570, 1487035437929625, 29470163960950720, 598896893196470516, 12504145259394103084, 268208623687371202156, 5911352523792061709194, 133914475861667199021171

Offset: 10

Author

Alois P. Heinz, Jul 25 2018

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 10..470

Crossrefs

Column k=5 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, 6)
    end:
a:= n-> coeff(b(n, 0$2), x, 5):
seq(a(n), n=10..30);