%I M3493 #21 Apr 03 2020 21:53:21
%S 1,1,4,14,129,1980,62611,2806490,158937213,10773251972,855658082615,
%T 78558949838723,8251166737356319,982806379842257309,
%U 131756174189661102281,19748565896506014747623,3289970433888731383271400,605948436052375098046655323,122796503871896458570959144266
%N Number of connected regular bipartite graphs of degree 4 with 2n nodes.
%D CRC Handbook of Combinatorial Designs, 1996, p. 648.
%D I. A. Faradzev, Constructive enumeration of combinatorial objects, pp. 131-135 of Problèmes combinatoires et théorie des graphes (Orsay, 9-13 Juillet 1976). Colloq. Internat. du C.N.R.S., No. 260, Centre Nat. Recherche Scient., Paris, 1978.
%D H. Gropp, On tactical configurations, regular bipartite graphs and (v,k,even)-designs, Discr. Math., 155 (1996), 81-98.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H B. D. McKay and E. Rogoyski, <a href="http://www.combinatorics.org/Volume_2/volume2.html#N3">Latin squares of order ten</a>, Electron. J. Combinatorics, 2 (1995) #N3.
%H M. Meringer, <a href="http://www.mathe2.uni-bayreuth.de/markus/reggraphs.html">Tables of Regular Graphs</a>
%F Inverse Euler transform of A333730. - _Andrew Howroyd_, Apr 03 2020
%Y Column 4 of A008326.
%Y Cf. A006823, A006825, A333730.
%K nonn,hard,nice
%O 4,3
%A _N. J. A. Sloane_
%E Terms a(12) and beyond from _Andrew Howroyd_, Apr 03 2020