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Number of tree-rooted toroidal maps with 2 faces and n vertices and without separating loops or isthmuses.
(Formerly M3708)
2

%I M3708 #13 Apr 04 2021 13:42:33

%S 4,120,1230,7424,32424,113584,338742,893220,2136618,4721728,9770904

%N Number of tree-rooted toroidal maps with 2 faces and n vertices and without separating loops or isthmuses.

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

%H T. R. S. Walsh and A. B. Lehman, <a href="http://dx.doi.org/10.1016/0095-8956(75)90050-7">Counting rooted maps by genus. III: Nonseparable maps</a>, J. Combinatorial Theory Ser. B 18 (1975), 222-259.

%F Empirical g.f.: 2*x*(x^6+8*x^5-13*x^4+22*x^3+105*x^2+40*x+2) / (x-1)^10. - _Colin Barker_, Apr 09 2013

%Y Cf. A006435, A006436, A006439.

%K nonn,more

%O 1,1

%A _N. J. A. Sloane_

%E Name clarified by _Andrew Howroyd_, Apr 04 2021