A343278 - OEIS

%I #13 Apr 20 2021 18:45:29

%S 1,1,1,3,7,25,90,350,1701,6951,42525,179487,1323652,5715424,49329280,

%T 216627840,2141764053,9528822303,106175395755,477297033785,

%U 5917584964655,26826851689001,366282500870286,1672162773483930,24930204590758260,114485073343744260

%N a(n) = Stirling2(n, ceiling(n/2)).

%C Number of partitions of an n-set into ceiling(n/2) nonempty subsets.

%t Table[StirlingS2[n, Ceiling[n/2]], {n, 0, 25}] (* _Amiram Eldar_, Apr 20 2021 *)

%o (PARI) a(n) = stirling(n, ceil(n/2), 2); \\ _Michel Marcus_, Apr 20 2021

%Y Bisection gives A007820 (even part),

%Y Cf. A048993, A129506, A343279.

%K nonn

%O 0,4

%A _Peter Luschny_, Apr 20 2021