A185134 - OEIS

%I #12 May 01 2014 02:37:07

%S 0,0,0,1,2,5,21,103,752,7385,91939,1345933,22170664,401399440,

%T 7887389438,166897766824,3781593764772

%N Number of, not necessarily connected, 3-regular simple graphs on 2n 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) = A185334(n) - A185335(n).

%F a(n) = A006924(n) + A185034(n).

%Y Not necessarily connected k-regular simple graphs girth exactly 4: A198314 (any k), A185644 (triangle); fixed k: A026797 (k=2), this sequence (k=3), A185144 (k=4).

%Y Not necessarily connected 3-regular simple graphs on 2n vertices with girth exactly g: A185130 (triangle); fixed g: A185133 (g=3), this sequence (g=4), A185135 (g=5), A185136 (g=6).

%K nonn,hard,more

%O 0,5

%A _Jason Kimberley_, Mar 21 2012