cp's OEIS Frontend

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

%I A215766 #4 Aug 23 2012 21:06:27
%S A215766 1,21,266,2898,31899,375375,4754200,64566645,936889954,14477748285,
%T A215766 237514188730,4124517063940,75606129579493,1459266319935423,
%U A215766 29585813267243475,628724462015327265,13976353234658809071,324398325664769299713,7848176443746842027187
%N A215766 Number of undirected labeled graphs on n nodes with exactly 6 cycle graphs as connected components.
%H A215766 Alois P. Heinz, <a href="/A215766/b215766.txt">Table of n, a(n) for n = 6..170</a>
%p A215766 T:= proc(n, k) option remember; `if`(k<0 or k>n, 0, `if`(n=0, 1,
%p A215766       add(binomial(n-1, i)*T(n-1-i, k-1)*ceil(i!/2), i=0..n-k)))
%p A215766     end:
%p A215766 a:= n-> T(n, 6):
%p A215766 seq (a(n), n=6..25);
%Y A215766 Column k=6 of A215771.
%K A215766 nonn
%O A215766 6,2
%A A215766 _Alois P. Heinz_, Aug 23 2012