A277364 Number of ways to partition a set of n elements into at most n/2 disjoint subsets.
1, 0, 1, 1, 8, 16, 122, 365, 2795, 11051, 86472, 422005, 3403127, 19628064, 164029595, 1084948961, 9433737120, 69998462014, 635182667816, 5199414528808, 49344452550230, 439841775811967, 4371727233798927, 42000637216351225, 437489737355466560, 4493269587087402967
Offset: 0
Keywords
Links
- Indranil Ghosh, Table of n, a(n) for n = 0..400
Programs
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Mathematica
Table[Sum[StirlingS2[n, k], {k, 0, n/2}], {n, 0, 25}] -
PARI
a(n) = sum(k=0, n\2, stirling(n, k, 2)); \\ Michel Marcus, Oct 11 2016
Formula
a(n) = Sum_{k=0..floor(n/2)} Stirling2(n,k).