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 A317286 Number of permutations of [n] with exactly six increasing runs of even length. 2

%I

%S 2702765,117248463,3118257980,73830310655,1708350797975,

%T 38581706239634,861226758827324,19346584353278646,439935779491790415,

%U 10146028258663315691,238129724283103648476,5701793180421505562215,139409020095464012520967,3483089247393778028230622

%N Number of permutations of [n] with exactly six increasing runs of even length.

%H Alois P. Heinz, <a href="/A317286/b317286.txt">Table of n, a(n) for n = 12..470</a>

%p b:= proc(u, o, t) option remember; series(`if`(u+o=0, x^t,

%p add(b(u+j-1, o-j, irem(t+1, 2)), j=1..o)+

%p add(b(u-j, o+j-1, 0)*x^t, j=1..u)), x, 7)

%p end:

%p a:= n-> coeff(b(n, 0\$2), x, 6):

%p seq(a(n), n=12..30);

%Y Column k=6 of A097592.

%K nonn

%O 12,1

%A _Alois P. Heinz_, Jul 25 2018

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Last modified June 27 19:20 EDT 2022. Contains 354898 sequences. (Running on oeis4.)