A006427 Number of rooted toroidal maps with 4 vertices and n faces and no isthmuses.

20, 1071, 26320, 431739, 5494896, 58677420, 550712668, 4681144391, 36786186216, 271221867098, 1896796135920, 12688048319278, 81709791432384, 509222462694582, 3083998029716868, 18213177504318335, 105186858991413976, 595499805083872458, 3311524095424508480

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

• 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 A343092.

Extensions

Name clarified and terms a(9) and beyond from Andrew Howroyd, Apr 05 2021