2,2
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=2..6.
T. R. S. Walsh and A. B. Lehman, Counting rooted maps by genus. II, J. Comb. Thy B13 (1972), 122-141.
Cf. A006302.
Sequence in context: A256811 A123035 A232033 * A219440 A219141 A220938
Adjacent sequences: A006300 A006301 A006302 * A006304 A006305 A006306
nonn,more
N. J. A. Sloane.
approved
