A165877 - OEIS

%I #19 May 20 2020 12:42:47

%S 0,0,0,0,0,0,0,0,1,5,1562,21617036,733460349818,42703733735064572,

%T 4073409466378991404239,613990076321940092226829047,

%U 141518698937232822678583027258225

%N Number of disconnected 7-regular (septic) graphs on 2n vertices.

%H N. J. A. Sloane, <a href="/transforms.txt">Transforms</a>

%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/SepticGraph.html">Septic Graph</a>

%F a = A165628 - A014377 = Euler_transformation(A014377) - A014377.

%F a(n)=D(2n, 7) in the triangle A068933.

%Y 7-regular simple graphs: A014377 (connected), this sequence(disconnected), A165628 (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), this sequence (k=7), A165878 (k=8), A185293 (k=9), A185203 (k=10), A185213 (k=11).

%K nonn,hard,more

%O 0,10

%A _Jason Kimberley_, Sep 28 2009

%E a(13)-a(16) from _Andrew Howroyd_, May 20 2020