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

7,2

Links

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

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

Adjacent sequences: A215854 A215855 A215856 * A215858 A215859 A215860

Keyword

nonn

Author

Alois P. Heinz, Aug 26 2012

Status

approved