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A215857
Number of simple labeled graphs on n nodes with exactly 7 connected components that are trees or cycles.
3
1, 28, 714, 17220, 424809, 11002068, 303874714, 9016296289, 288135739892, 9913826194272, 366486926833846, 14513217676764534, 613646633464214863, 27609928896732666760, 1317652578222779606269, 66497975770225498765728, 3538905411811229060814213
OFFSET
7,2
LINKS
EXAMPLE
a(8) = 28: each graph has one 2-node tree and 6 1-node trees and C(8,2) = 28.
MAPLE
T:= proc(n, k) option remember; `if`(k<0 or k>n, 0,
`if`(n=0, 1, add(binomial(n-1, i)*T(n-1-i, k-1)*
`if`(i<2, 1, i!/2 +(i+1)^(i-1)), i=0..n-k)))
end:
a:= n-> T(n, 7):
seq(a(n), n=7..25);
CROSSREFS
Column k=7 of A215861.
The unlabeled version is A215987.
Sequence in context: A160141 A331476 A239408 * A185987 A004293 A012808
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 26 2012
STATUS
approved