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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..242

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: A074702 A197717 A277456 * A152282 A153255 A015084

Adjacent sequences: A317137 A317138 A317139 * A317141 A317142 A317143

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Jul 22 2018

STATUS

approved

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Last modified January 29 00:02 EST 2023. Contains 359905 sequences. (Running on oeis4.)