A270965 Number of set partitions of [2n] having exactly n pairs (m,m+1) such that m+1 is in some block b and m is in block b+1.

1, 0, 0, 1, 10, 127, 1650, 23258, 361154, 6131236, 113042841, 2248848796, 47985568177, 1092290052791, 26397613960112, 674479517926073, 18153075875657428, 512977569857121559, 15176209471995304906, 468847646698743759887, 15090613008931715532300

Offset: 0

Author

Alois P. Heinz, Mar 26 2016

Keywords

• nonn

Examples

			a(3) = 1: 136|25|4.
a(4) = 10: 1358|247|6, 1368|257|4, 136|258|47, 136|25|48|7, 138|257|46, 13|258|47|6, 138|27|46|5, 158|247|36, 15|248|37|6, 18|247|36|5.
a(5) = 127: 1247(10)|369|58, 1247|36(10)|59|8, 124(10)|369|58|7, ..., 1(10)|269|358|47, 1|26(10)|359|48|7, 1(10)|29|358|47|6.
		

Links

• Wikipedia, Partition of a set

Crossrefs

Cf. A270953.

Formula

a(n) = A270953(2n,n).