4,3

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

CRC Handbook of Combinatorial Designs, 1996, p. 648.

I. A. Faradzev, Constructive enumeration of combinatorial objects, pp. 131-135 of Probl\`{e}mes combinatoires et th\'{e}orie des graphes (Orsay, 9-13 Juillet 1976). Colloq. Internat. du C.N.R.S., No. 260, Centre Nat. Recherche Scient., Paris, 1978.

H. Gropp, On tactical configurations, regular bipartite graphs and (v,k,even)-designs, Discr. Math., 155 (1996), 81-98.

B. D. McKay and E. Rogoyski, Latin squares of order ten, Electron. J. Combinatorics, 2 (1995) #N3.

M. Meringer, Tables of Regular Graphs

Cf. A006823, A006825.

A column of triangle A008326.

Sequence in context: A065062 A137048 A137056 this_sequence A162077 A111266 A098851

Adjacent sequences: A006821 A006822 A006823 this_sequence A006825 A006826 A006827

nonn,hard,nice

N. J. A. Sloane (njas(AT)research.att.com).