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A317140
Number of permutations of [2n+1] with exactly n increasing runs of length two.
3
1, 4, 43, 906, 31493, 1629248, 117248463, 11190963430, 1367267690953, 208031951035452, 38563334673062963, 8554779137299629314, 2237467931691025532493, 681305299577272105281016, 238929711424864185326131543, 95603626135129502838914478558
OFFSET
0,2
LINKS
FORMULA
a(n) = A317139(2n+1) = A097592(2n+1,n).
a(n) + n == 1 (mod 2).
EXAMPLE
a(1) = 4: 132, 213, 231, 312.
CROSSREFS
Bisection (odd part) of A317139.
Cf. A097592.
Sequence in context: A197717 A277456 A377743 * A152282 A153255 A015084
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jul 22 2018
STATUS
approved