A287253 Number of set partitions of [n] such that all absolute differences between least elements of consecutive blocks are <= three.

1, 1, 2, 5, 15, 51, 191, 780, 3440, 16249, 81736, 435796, 2453100, 14529728, 90294625, 587256087, 3988153356, 28223370977, 207745253237, 1587804229045, 12581186077773, 103197641796678, 875085283793768, 7661468372063681, 69173450911547978, 643354845906697516

Offset: 0

Author

Alois P. Heinz, May 22 2017

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..586
• Wikipedia, Partition of a set

Crossrefs

Column k=3 of A287216.

Cf. A000110.

Formula

a(n) = A287216(n,3).

a(n) = A000110(n) for n <= 4.