3,2

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

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 171.

E. M. Palmer and R. W. Robinson, Enumeration under two representations of the wreath product, Acta Math., 131 (1973), 123-143.

Cf. A003223, A003225.

Sequence in context: A027851 A120765 A051812 this_sequence A156310 A142725 A070387

Adjacent sequences: A003221 A003222 A003223 this_sequence A003225 A003226 A003227

nonn,easy,more

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