%I #19 May 20 2020 12:42:56

%S 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,7,100,10901,3470736,

%T 1473822243,734843169811,423929978716908,281768931380519766,

%U 215039290728074333738,187766225244288486398132,186874272297562916477691894,211165081721567703008217979077

%N Number of disconnected 8-regular simple graphs on n vertices.

%H Jason Kimberley, <a href="/wiki/User:Jason_Kimberley/A068933">Disconnected regular graphs (with girth at least 3)</a>

%H Jason Kimberley, <a href="/wiki/User:Jason_Kimberley/D_k-reg_girth_ge_g_index">Index of sequences counting disconnected k-regular simple graphs with girth at least g</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/DisconnectedGraph.html">Disconnected Graph</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/OcticGraph.html">Octic Graph</a>

%F a = A180260 - A014378 = Euler_transformation(A014378) - A014378.

%F a(n) = D(n, 8) in the triangle A068933.

%e The a(18)=1 graph is K_9+K_9.

%Y 8-regular simple graphs: A014378 (connected), this sequence (disconnected), A180260 (not necessarily connected).

%Y Disconnected regular simple graphs: A068932 (any degree), A068933 (triangular array), specified degree k: A165652 (k=2), A165653 (k=3), A033483 (k=4), A165655 (k=5), A165656 (k=6), A165877 (k=7), this sequence (k=8), A185293 (k=9), A185203 (k=10), A185213 (k=11).

%K nonn,hard

%O 0,21

%A _Jason Kimberley_, Sep 29 2009

%E Terms a(26) and beyond from _Andrew Howroyd_, May 20 2020