2,1

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

R. C. Read, Some Enumeration Problems in Graph Theory. Ph.D. Dissertation, Department of Mathematics, Univ. London, 1958.

Sequence in context: A112945 A080295 A084108 this_sequence A006712 A099057 A123278

Adjacent sequences: A006710 A006711 A006712 this_sequence A006714 A006715 A006716

nonn

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