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Number of disconnected 6-regular (sextic) graphs on n vertices.
12

%I #23 May 20 2020 12:42:41

%S 0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,5,25,297,8199,377004,22014143,

%T 1493574756,114880777582,9919463450855,955388277929620,

%U 102101882472479938,12050526046888229845,1563967741064673811531,222318116370232302781485,34486536277291555593662301,5817920265098158804699762770

%N Number of disconnected 6-regular (sextic) graphs on n 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/DisconnectedGraph.html">Disconnected Graph</a>

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

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

%F a = A165627 - A006822 = Euler_transformation(A006822) - A006822.

%F a(n) = D(n, 6) in the triangle A068933.

%Y 6-regular simple graphs: A006822 (connected), this sequence (disconnected), A165627 (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), this sequence (k=6), A165877 (k=7), A165878 (k=8), A185293 (k=9), A185203 (k=10), A185213 (k=11).

%K nonn,hard

%O 0,17

%A _Jason Kimberley_, Sep 28 2009

%E Terms a(25) and beyond from _Andrew Howroyd_, May 20 2020