1,2
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).
Table of n, a(n) for n=1..10.
Sequence in context: A114198 A055836 A076177 * A126033 A007863 A030823
Adjacent sequences: A007161 A007162 A007163 * A007165 A007166 A007167
nonn
N. J. A. Sloane.
approved
