R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1976.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Walsh, T. R. S.; Counting labeled three-connected and homeomorphically irreducible two-connected graphs. J. Combin. Theory Ser. B 32 (1982), no. 1, 1-11.