A270958 Number of set partitions of [n] having exactly four pairs (m,m+1) such that m+1 is in some block b and m is in block b+1.

10, 174, 1783, 15158, 121464, 965616, 7776877, 64017975, 540759958, 4695640591, 41947390960, 385584558062, 3646493831801, 35466401895010, 354594794206614, 3642294128252241, 38413175987708429, 415694601586123128, 4612983463942832627, 52460139965678764835

Offset: 8

Author

Alois P. Heinz, Mar 26 2016

Keywords

• nonn

Examples

			a(8) = 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.
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 8..220
• Wikipedia, Partition of a set

Crossrefs

Column k=4 of A270953.