%I #12 Apr 07 2018 03:18:20
%S 0,0,0,0,0,0,0,0,1,1,1,1,4,4,10,10,20,10,20,35,20,35,56,56,56,84,84,
%T 120,84,120,165,220,220,220,286,286,286,364,455,455,560,455,680,560,
%U 680,680,816,969,1140,969
%N Ono prime weight function divided by 6.
%H Ken Ono and Scott Ahlgren, <a href="http://www.mathcs.emory.edu/~ono/publications-cv/pdfs/070.pdf">Weierstrass points on X0(p) and supersingular j-invariants</a>, Mathematische Annalen 325, 2003, pp. 355-368.
%t g[1] = 1; g[2] = 1;
%t g[n_] := (Prime[n] - 13)/12 /; Mod[Prime[n], 12] - 1 == 0;
%t g[n_] := (Prime[n] - 5)/12 /; Mod[Prime[n], 12] - 5 == 0;
%t g[n_] := (Prime[n] - 7)/12 /; Mod[Prime[n], 12] - 7 == 0;
%t g[n_] := (Prime[n] + 1)/12 /; Mod[Prime[n], 12] - 11 == 0;
%t Table[g[n]*(g[n]^2 - 1)/6, {n, 1, 50}]
%o (PARI) a(n) = {if (n < 3, g = 1, p = prime(n); m = p % 12; g = if (m==1, (p-13)/12, if (m==5, (p-5)/12, if (m==7, (p-7)/12, if (m==11, (p+1)/12))))); g*(g^2-1)/6;} \\ _Michel Marcus_, Apr 06 2018
%Y Cf. A116563.
%K nonn,uned,obsc
%O 1,13
%A _Roger L. Bagula_, Mar 18 2006
%E Offset corrected by _Michel Marcus_, Apr 06 2018