login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

Number of non-singleton blocks in the n-th set partition (A231428).
2

%I #11 Nov 28 2014 22:18:49

%S 0,1,1,1,1,1,2,1,2,1,1,2,1,1,1,1,2,2,2,2,1,2,2,2,2,1,2,1,2,2,2,2,1,2,

%T 1,2,1,1,2,2,2,2,1,2,1,2,1,1,2,1,1,1,1,2,2,2,2,2,3,2,3,2,2,3,2,2,2,1,

%U 2,2,2,2,2,3,2,3,2,2,3,2,2,2

%N Number of non-singleton blocks in the n-th set partition (A231428).

%H Tilman Piesk, <a href="/A249615/b249615.txt">Table of n, a(n) for n = 0..9999</a>

%H Tilman Piesk, <a href="https://commons.wikimedia.org/wiki/File:Set_partitions_5;_list.svg">Illustrated list of the first 52 equivalence relations</a>

%H Tilman Piesk, <a href="https://en.wikiversity.org/wiki/Permutations_and_partitions_in_the_OEIS">Permutations and partitions in the OEIS</a> (Wikiversity)

%e The 6th set partition has 2 non-singleton blocks {1,4} and {2,3}. So a(6) = 2.

%Y Cf. A231428, A249616

%K nonn

%O 0,7

%A _Tilman Piesk_, Nov 02 2014