%I #4 Aug 23 2012 21:06:27

%S 1,21,266,2898,31899,375375,4754200,64566645,936889954,14477748285,

%T 237514188730,4124517063940,75606129579493,1459266319935423,

%U 29585813267243475,628724462015327265,13976353234658809071,324398325664769299713,7848176443746842027187

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

%H Alois P. Heinz, <a href="/A215766/b215766.txt">Table of n, a(n) for n = 6..170</a>

%p T:= proc(n, k) option remember; `if`(k<0 or k>n, 0, `if`(n=0, 1,

%p add(binomial(n-1, i)*T(n-1-i, k-1)*ceil(i!/2), i=0..n-k)))

%p end:

%p a:= n-> T(n, 6):

%p seq (a(n), n=6..25);

%Y Column k=6 of A215771.

%K nonn

%O 6,2

%A _Alois P. Heinz_, Aug 23 2012