5,2

Since the 9-regular graph with the least number of vertices is K_10, there are no disconnected 9-regular graphs with less than 20 vertices. Thus for n<20 this sequence also gives the number of all 9-regular graphs on 2n vertices. [From Jason Kimberley (Jason.Kimberley(AT)newcastle.edu.au), Sep 25 2009]

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.

M. Meringer, Tables of Regular Graphs

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

Connected regular graphs of degree k: A002851 (k=3), A006820 (k=4), A006821 (k=5), A006822 (k=6), A014377 (k=7), A014378 (k=8), A014381 (k=9), A014382 (k=10), A014384 (k=11).

Adjacent sequences: A014378 A014379 A014380 this_sequence A014382 A014383 A014384

Sequence in context: A013790 A058452 A058456 this_sequence A034995 A109464 A120352

nonn,bref,more,hard

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

a(8) from Jason Kimberley (Jason.Kimberley(AT)newcastle.edu.au), Sep 25 2009