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A317283 Number of permutations of [n] with exactly three increasing runs of even length. 2
61, 906, 8965, 94398, 1088575, 12625694, 150890533, 1914036434, 25485825638, 353702731940, 5141233861254, 78259458749608, 1243051438276365, 20579839942072222, 354951501710697119, 6367683567830126402, 118640486378324764141, 2293339890430027143606 (list; graph; refs; listen; history; text; internal format)
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

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Last modified March 26 04:32 EDT 2019. Contains 321481 sequences. (Running on oeis4.)