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A321526
Number of partitioned graphs on n labeled nodes.
1
1, 4, 40, 960, 53248, 6651904, 1839202304, 1111322787840, 1453210774536192, 4080507553002291200, 24448060793158379765760, 310908581955001382242091008, 8355018414502495124631718985728, 472643828352464917980832865510752256
OFFSET
1,2
COMMENTS
Bell numbers (partitions of the nodes) multiplied by the number of graphs on the nodes.
LINKS
FORMULA
a(n) = A000110(n) * A006125(n).
a(n) = Bell(n) * 2^binomial(n, 2).
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
Sequence in context: A211040 A012957 A012977 * A361057 A013108 A173945
KEYWORD
nonn
AUTHOR
Peter Baumgartner, Nov 12 2018
STATUS
approved