A317284 Number of permutations of [n] with exactly four increasing runs of even length.

1385, 31493, 460929, 6632158, 99592344, 1489928080, 22566676855, 354404597721, 5758011600442, 96477356811365, 1673128285327455, 30065282456829860, 558998263719383722, 10749166166477149832, 213755085162112473899, 4392507334767609209209, 93197430506980061714657

Offset

8,1

Links

Alois P. Heinz, Table of n, a(n) for n = 8..471

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, 5)
    end:
a:= n-> coeff(b(n, 0$2), x, 4):
seq(a(n), n=8..30);

Crossrefs

Column k=4 of A097592.

Sequence in context: A345526 A345780 A302900 * A060062 A181991 A212222

Adjacent sequences: A317281 A317282 A317283 * A317285 A317286 A317287

Keyword

nonn

Author

_Alois P. Heinz_, Jul 25 2018

Status

approved