A185144 - OEIS

A185144

Number of not necessarily connected 4-regular simple graphs on n vertices with girth exactly 4.

%I #25 Feb 22 2013 10:47:04

%S 0,0,0,0,0,0,0,0,1,0,2,2,12,31,220,1606,16829,193900,2452820,32670331,

%T 456028487,6636066126,100135577863,1582718910743

%N Number of not necessarily connected 4-regular simple graphs on n vertices with girth exactly 4.

%H Jason Kimberley, <a href="/wiki/User:Jason_Kimberley/E_k-reg_girth_eq_g_index">Index of sequences counting not necessarily connected k-regular simple graphs with girth exactly g</a>

%F a(n) = A184944(n) + A185044(n) = A185140(n,4).

%Y Not necessarily connected k-regular simple graphs girth exactly 4: A198314 (any k), A185644 (triangle); fixed k: A026797 (k=2), A185134 (k=3), this sequence (k=4).

%Y A185143 (g=3), A185144 (g=4).

%Y Not necessarily connected 4-regular simple graphs with girth exactly g: A185140 (triangle); fixed g: A185143 (g=3), this sequence (g=4).

%K nonn,hard,more

%O 0,11

%A _Jason Kimberley_, Nov 04 2011

%E Corrected by _Jason Kimberley_, Jan 03 2013