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A317285
Number of permutations of [n] with exactly five increasing runs of even length.
2
50521, 1629248, 32918922, 617859020, 11668739836, 217316513198, 4043244094251, 76688877688570, 1487035437929625, 29470163960950720, 598896893196470516, 12504145259394103084, 268208623687371202156, 5911352523792061709194, 133914475861667199021171
OFFSET
10,1
LINKS
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);
CROSSREFS
Column k=5 of A097592.
Sequence in context: A231918 A029823 A302902 * A253032 A251486 A376929
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jul 25 2018
STATUS
approved