A006433 Number of tree-rooted planar maps with 4 vertices and n faces and no isthmuses.

0, 4, 175, 3324, 42469, 429120, 3711027, 28723640, 204598130, 1366223880, 8664086470, 52673351080, 309164754285, 1761471681568, 9783594370723, 53154274959360, 283267669144390, 1484104565936920, 7658877239935362, 38993558097982312, 196127054929939810

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Comments

A map without isthmuses can also be called bridgeless.

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. See Table VIIIb.

Crossrefs

A diagonal of A342987.

Extensions

Terms a(12) and beyond from Andrew Howroyd, Apr 06 2021