A215766 Number of undirected labeled graphs on n nodes with exactly 6 cycle graphs as connected components.

1, 21, 266, 2898, 31899, 375375, 4754200, 64566645, 936889954, 14477748285, 237514188730, 4124517063940, 75606129579493, 1459266319935423, 29585813267243475, 628724462015327265, 13976353234658809071, 324398325664769299713, 7848176443746842027187

Offset

6,2

Links

Alois P. Heinz, Table of n, a(n) for n = 6..170

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)*ceil(i!/2), i=0..n-k)))
    end:
a:= n-> T(n, 6):
seq (a(n), n=6..25);

Crossrefs

Column k=6 of A215771.

Sequence in context: A000770 A327507 A133105 * A320819 A360499 A228215

Adjacent sequences: A215763 A215764 A215765 * A215767 A215768 A215769

Keyword

nonn

Author

Alois P. Heinz, Aug 23 2012

Status

approved