A372764 Number of partitions of [n] having exactly two blocks of minimal size.

0, 0, 1, 0, 9, 10, 70, 336, 1393, 6210, 41331, 228635, 1315974, 8779134, 61675419, 434566510, 3237964993, 25386526258, 207569429548, 1756564362651, 15418550267179, 140015129879331, 1316198207272686, 12786566843038549, 128035136707876270, 1319513338177755510

Offset: 0

Author

Alois P. Heinz, May 12 2024

Keywords

• nonn

Examples

			a(2) = 1: 1|2.
a(4) = 9: 12|34, 12|3|4, 13|24, 13|2|4, 14|23, 1|23|4, 14|2|3, 1|24|3, 1|2|34.
a(5) = 10: 123|4|5, 124|3|5, 125|3|4, 134|2|5, 135|2|4, 1|234|5, 1|235|4, 145|2|3, 1|245|3, 1|2|345.
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..576
• Wikipedia, Partition of a set

Crossrefs

Column k=2 of A372762.

Programs

Maple

b:= proc(n, m, t) option remember; `if`(n=0,
     `if`(t=2, 1, 0), add(binomial(n-1, j-1)*b(n-j, min(j, m),
     `if`(j b(n$2, 0):
seq(a(n), n=0..25);