A317283 Number of permutations of [n] with exactly three increasing runs of even length.

61, 906, 8965, 94398, 1088575, 12625694, 150890533, 1914036434, 25485825638, 353702731940, 5141233861254, 78259458749608, 1243051438276365, 20579839942072222, 354951501710697119, 6367683567830126402, 118640486378324764141, 2293339890430027143606

Offset

6,1

Links

Alois P. Heinz, Table of n, a(n) for n = 6..472

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, 4)
    end:
a:= n-> coeff(b(n, 0$2), x, 3):
seq(a(n), n=6..30);

Crossrefs

Column k=3 of A097592.

Sequence in context: A093473 A000506 A008358 * A264306 A138790 A057534

Adjacent sequences: A317280 A317281 A317282 * A317284 A317285 A317286

Keyword

nonn

Author

Alois P. Heinz, Jul 25 2018

Status

approved