A215857 Number of simple labeled graphs on n nodes with exactly 7 connected components that are trees or cycles.

1, 28, 714, 17220, 424809, 11002068, 303874714, 9016296289, 288135739892, 9913826194272, 366486926833846, 14513217676764534, 613646633464214863, 27609928896732666760, 1317652578222779606269, 66497975770225498765728, 3538905411811229060814213

Offset: 7

Author

Alois P. Heinz, Aug 26 2012

Keywords

• nonn

Examples

			a(8) = 28: each graph has one 2-node tree and 6 1-node trees and C(8,2) = 28.
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 7..145

Crossrefs

Column k=7 of A215861.

The unlabeled version is A215987.

Programs

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);