OFFSET
1,2
COMMENTS
Bell numbers (partitions of the nodes) multiplied by the number of graphs on the nodes.
LINKS
Peter Baumgartner, Table of n, a(n) for n = 1..50
EXAMPLE
a(1) = 1 * 1; a(2) = 2 * 2, a(3) = 5 * 8, a(4) = 15 * 64.
MATHEMATICA
a[n_] := BellB[n]*2^Binomial[n, 2]; Array[a, 14] (* Amiram Eldar, Nov 12 2018 *)
PROG
(PARI) bell(n)={sum(k=0, n, stirling(n, k, 2))}
a(n)=bell(n)*2^binomial(n, 2) \\ Andrew Howroyd, Nov 12 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Baumgartner, Nov 12 2018
STATUS
approved