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Number of regular bipartite simple graphs on n nodes.
1

%I #13 Feb 21 2024 12:33:02

%S 1,1,2,1,3,1,4,1,6,1,8,1,18,1,40,1,230,1,4296,1,431206,1,162267272,1,

%T 201636689771,1,777816803942186,1,9865957936943931964,1,

%U 395886667549681689591841,1,53716176608076643470621234239,1,23524515269630339982914646821899537,1,35682168849414944013547274452501768506834,1

%N Number of regular bipartite simple graphs on n nodes.

%C A graph must be regular and bipartite to be a semisymmetric graph.

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

%F a(2*n + 1) = 1, a(2*n) = A008324(n). - _Andrew Howroyd_, Sep 05 2018

%Y Cf. A008323, A008324, A008327.

%K nonn

%O 0,3

%A _Eric W. Weisstein_, Aug 13 2003

%E a(10)-a(19) from _Andrew Howroyd_, Sep 05 2018

%E a(0)=1 prepended and a(20) onwards added by _Andrew Howroyd_, Feb 21 2024