A275290 Number of set partitions of [n] with symmetric block size list of length five.

1, 3, 22, 86, 470, 2066, 10299, 47503, 229792, 1081851, 5189068, 24671320, 118223765, 565269659, 2713032552, 13022313334, 62644482305, 301600159952, 1454293747517, 7019496361595, 33922782653124, 164099194834163, 794642770006896, 3851565096708617

Offset: 5

Author

Alois P. Heinz, Jul 22 2016

Keywords

• nonn

Examples

			a(6) = 3: 1|2|34|5|6, 1|2|35|4|6, 1|2|36|4|5.
a(7) = 22: 12|3|4|5|67, 13|2|4|5|67, 1|23|4|56|7, 1|23|4|57|6, 14|2|3|5|67, 1|24|3|56|7, 1|24|3|57|6, 1|2|345|6|7, 1|2|346|5|7, 1|2|347|5|6, 15|2|3|4|67, 1|25|3|46|7, 1|25|3|47|6, 1|2|356|4|7, 1|2|357|4|6, 1|26|3|45|7, 1|27|3|45|6, 16|2|3|4|57, 1|26|3|47|5, 1|2|367|4|5, 1|27|3|46|5, 17|2|3|4|56.
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 5..500
• Vaclav Kotesovec, Recurrence (of order 7)
• Wikipedia, Partition of a set

Crossrefs

Column k=5 of A275281.

Formula

a(n) ~ 5^n / (96*Pi*n). - Vaclav Kotesovec, Aug 02 2016