A120699 - OEIS

%I #13 Feb 18 2024 01:32:54

%S 0,1,2,2,3,3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,

%T 5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,

%U 5,5,5,5,5,5,5,5,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6

%N Lengths of set partitions.

%C Each n occurs Bell(n) times.

%H Paolo Xausa, <a href="/A120699/b120699.txt">Table of n, a(n) for n = 0..10000</a>

%F Sum_{n>=1} (-1)^(n+1)/a(n) = Pi/(6*sqrt(3)) + log(3)/2. - _Amiram Eldar_, Feb 18 2024

%t Flatten[Array[PadRight[{}, BellB[#], #]&, 7, 0]] (* _Paolo Xausa_, Feb 13 2024 *)

%Y Cf. A000110, A120698.

%K nonn

%O 0,3

%A _Franklin T. Adams-Watters_, Jun 28 2006