A274875 Number of set partitions of [2n] into exactly n blocks such that all odd elements are in blocks with an odd index and all even elements are in blocks with an even index.

1, 0, 1, 3, 35, 226, 3632, 36780, 770481, 10677444, 277114769, 4882093495, 151410615066, 3238949008872, 116936529884088, 2943848265346408, 121318690777898613, 3513774792447267240, 162794429514873454259, 5332375501915984656921, 274393112247007415104839

Offset

0,4

Links

Alois P. Heinz, Table of n, a(n) for n = 0..300

Formula

a(n) = A274537(2n,n).

Example

a(2) = 1: 13|24.
a(3) = 3: 13|246|5, 15|246|3, 1|246|35.
a(4) = 35: 135|246|7|8, 137|246|5|8, 13|246|57|8, 137|248|5|6, 137|24|5|68, 13|248|57|6, 13|24|57|68, 157|246|3|8, 15|246|37|8, 157|248|3|6, 157|24|3|68, 15|248|37|6, 15|24|37|68, 17|246|35|8, 1|246|357|8, 17|248|35|6, 17|24|35|68, 1|248|357|6, 1|24|357|68, 157|268|3|4, 157|26|3|48, 15|268|37|4, 15|26|37|48, 157|28|3|46, 157|2|3|468, 15|28|37|46, 15|2|37|468, 17|268|35|4, 17|26|35|48, 1|268|357|4, 1|26|357|48, 17|28|35|46, 17|2|35|468, 1|28|357|46, 1|2|357|468.

Crossrefs

Cf. A274537.

Sequence in context: A133710 A130061 A368391 * A061548 A019273 A271209

Adjacent sequences: A274872 A274873 A274874 * A274876 A274877 A274878

Keyword

nonn

Author

Alois P. Heinz, Jul 09 2016

Status

approved