A006432 Number of tree-rooted planar maps with 3 vertices and n faces and no isthmuses.

0, 3, 60, 650, 5352, 37681, 239752, 1421226, 7996160, 43219990, 226309800, 1154900708, 5769562736, 28312118565, 136830224464, 652656300122, 3077631550512, 14367512295274, 66478236840680, 305161336656876, 1390869368495728, 6298727501142218, 28358908010334960

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

References

• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..100
• T. R. S. Walsh and A. B. Lehman, Counting rooted maps by genus. III: Nonseparable maps, J. Combinatorial Theory Ser. B 18 (1975), 222-259.

Crossrefs

A diagonal of A342987.

Formula

a(n) seems to be divisible by n+1. - Ralf Stephan, Sep 01 2003

Extensions

Name clarified and terms a(13) and beyond from Andrew Howroyd, Apr 06 2021