OFFSET
2,1
COMMENTS
It would be nice to have a more precise definition for this ancient sequence from the Walsh-Lehman paper. - N. J. A. Sloane, Jun 05 2017
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
T. R. S. Walsh and A. B. Lehman, Counting rooted maps by genus. II, J. Comb. Thy B13 (1972), 122-141.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
STATUS
approved