1,3
R. C. Read, On the enumeration of a class of plane multigraphs, Aequat. Math., 31 (1986), 47-63.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Sequence in context: A104190 A152661 A177066 * A171455 A136722 A085615
Adjacent sequences: A007167 A007168 A007169 * A007171 A007172 A007173
nonn
N. J. A. Sloane (njas(AT)research.att.com).
