A006433 - OEIS

A006433

Number of tree-rooted planar maps with 4 vertices and n faces and no isthmuses.
(Formerly M3720)

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

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.

Sequence in context: A081783 A222921 A318216 * A251695 A343610 A113254

Adjacent sequences: A006430 A006431 A006432 * A006434 A006435 A006436

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

EXTENSIONS

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

STATUS

approved