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A343278
a(n) = Stirling2(n, ceiling(n/2)).
1
1, 1, 1, 3, 7, 25, 90, 350, 1701, 6951, 42525, 179487, 1323652, 5715424, 49329280, 216627840, 2141764053, 9528822303, 106175395755, 477297033785, 5917584964655, 26826851689001, 366282500870286, 1672162773483930, 24930204590758260, 114485073343744260
OFFSET
0,4
COMMENTS
Number of partitions of an n-set into ceiling(n/2) nonempty subsets.
MATHEMATICA
Table[StirlingS2[n, Ceiling[n/2]], {n, 0, 25}] (* Amiram Eldar, Apr 20 2021 *)
PROG
(PARI) a(n) = stirling(n, ceil(n/2), 2); \\ Michel Marcus, Apr 20 2021
CROSSREFS
Bisection gives A007820 (even part),
Sequence in context: A148739 A129084 A287892 * A002870 A096579 A350650
KEYWORD
nonn
AUTHOR
Peter Luschny, Apr 20 2021
STATUS
approved