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. A003224, A003225.

Sequence in context: A022492 A123429 A006841 this_sequence A061417 A153921 A060315

Adjacent sequences: A003220 A003221 A003222 this_sequence A003224 A003225 A003226

nonn,easy,more

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