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Number of set partitions of [n] such that all absolute differences between least elements of consecutive blocks are <= four.
4

%I #6 May 22 2017 11:48:45

%S 1,1,2,5,15,52,202,857,3933,19373,101755,566712,3331349,20592862,

%T 133439286,903926271,6385918342,46950260915,358560107124,

%U 2839638581291,23285101241537,197425160416845,1728548417051752,15610025975013920,145242705457704688

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

%H Alois P. Heinz, <a href="/A287254/b287254.txt">Table of n, a(n) for n = 0..584</a>

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Partition_of_a_set">Partition of a set</a>

%F a(n) = A287216(n,4).

%F a(n) = A000110(n) for n <= 5.

%Y Column k=4 of A287216.

%Y Cf. A000110.

%K nonn

%O 0,3

%A _Alois P. Heinz_, May 22 2017