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Number of Q-graphs with 2n edges.
(Formerly M1296)
0

%I M1296 #14 Nov 08 2017 02:25:24

%S 1,2,4,16,89,579,3989,28630,210865,1584308,12091902,93483120,

%T 730503054,5760438853,45780146521,366304396662,2948412461685,

%U 23857049238752,193944769559906,1583294537879106,12974430494985262,106685110047676402

%N Number of Q-graphs with 2n edges.

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H R. C. Read, <a href="http://dx.doi.org/10.1007/BF02188172">On the enumeration of a class of plane multigraphs</a>, Aequat. Math. 31 (1986) no 1, 47-63.

%F a(1) = 1, a(n) = A007170(n) + (A003169(n-1) + A007165(n-1)) / 2. - _Sean A. Irvine_, Nov 07 2017

%Y Cf. A003169, A007165, A007170.

%K nonn

%O 1,2

%A _N. J. A. Sloane_.

%E a(9) corrected and more terms from _Sean A. Irvine_, Nov 07 2017