login
a(n) = n^n * (n^2 - 1)/24.
3

%I #7 Jul 03 2018 21:19:17

%S 9,160,3125,68040,1647086,44040192,1291401630,41250000000,

%T 1426558353055,53125098504192,2120125746145771,90285055457658880,

%U 4087009643554687500,195996655783163985920,9926883142636041170124,529537075346699234869248

%N a(n) = n^n * (n^2 - 1)/24.

%C For n >= 3, a(n) is the number of nonequivalent primitive meromorphic functions with one pole of order n on a Riemann surface of genus 1.

%D B. Shapiro, M. Shapiro and A. Vainshtein, Ramified coverings of S^2 with one degenerate branching point and enumeration of edge-ordered graphs, Amer. Math. Soc. Transl., Vol. 180 (1997), pp. 219-227.

%H Harry J. Smith, <a href="/A060348/b060348.txt">Table of n, a(n) for n = 3..200</a>

%o (PARI) { for (n=3, 200, write("b060348.txt", n, " ", n^n * (n^2 - 1)/24); ) } \\ _Harry J. Smith_, Jul 04 2009

%Y Cf. A007830, A060349.

%K nonn

%O 3,1

%A Noam Katz (noamkj(AT)hotmail.com), Mar 30 2001