A006387 Number of unsensed genus 1 maps with n edges.

0, 0, 1, 6, 40, 320, 2946, 29364, 309558, 3365108, 37246245, 416751008, 4696232371, 53186743416, 604690121555, 6896534910612, 78867385697513, 904046279771682, 10384916465797240, 119522063788612992, 1378014272286250059

Offset: 0

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

• Evgeniy Krasko and Alexander Omelchenko, Enumeration of Unsensed Orientable Maps on Surfaces of a Given Genus, arXiv:1712.10139 [math.CO], 2017.
• Timothy R. Walsh, Space-efficient generation of nonisomorphic maps and hypermaps
• Timothy R. Walsh, Generating nonisomorphic maps without storing them, SIAM J. Algebraic Discrete Methods 4 (1983), no. 2, 161-178.
• T. R. Walsh, Space-Efficient Generation of Nonisomorphic Maps and Hypermaps, J. Int. Seq. 18 (2015) # 15.4.3

Crossrefs

Column k=1 of A379439.

Cf. A006300 (rooted), A006385 (planar), A006386 (sensed), A214814, A214815, A214816.

Extensions

a(12)-a(20) from Evgeniy Krasko, Sep 17 2017