OFFSET
0,2
REFERENCES
Ken Ono, The Web of Modularity: Arithmetic of the Coefficients of Modular Forms and q-series, CBMS Regional Conference Series in Mathematics, vol. 102, American Mathematical Society, Providence, RI, 2004.
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..366
FORMULA
From Seiichi Manyama, Jun 27 2017: (Start)
Let j_0 = 1 and j_1 = j - 744. Define j_m by j_m = j1 | T_0(m), where T_0(m) = mT_{m, 0} is the normalized m-th weight zero Hecke operator. a(n) = j_n(i).
G.f.: Sum_{n >= 0} j_n(i)*q^n. (End)
a(n) ~ 2 * exp(2*Pi*n). - Vaclav Kotesovec, Jun 28 2017
G.f.: -q*j'/(j-1728) where j is the elliptic modular invariant (A000521). - Seiichi Manyama, Jul 12 2017
EXAMPLE
G.f.: 1 + 984*q + 574488*q^2 + 307081056*q^3 + 164453203992*q^4 + 88062998451984*q^5 + 47157008244215904*q^6 + ...
From Seiichi Manyama, Jun 27 2017: (Start)
a(0) = j_0(i) = 1,_
a(1) = j_1(i) = -744 + 1728^1 = 984,
a(2) = j_2(i) = 159768 - 1488*1728^1 + 1728^2 = 574488. (End)
MATHEMATICA
nmax = 20; CoefficientList[Series[(1 + 480*Sum[DivisorSigma[7, k]*x^k, {k, 1, nmax}])/(1 - 504*Sum[DivisorSigma[5, k]*x^k, {k, 1, nmax}]), {x, 0, nmax}], x] (* Vaclav Kotesovec, Jun 28 2017 *)
terms = 12; Ei[n_] = 1-(2n/BernoulliB[n]) Sum[k^(n-1) x^k/(1-x^k), {k, terms}]; CoefficientList[Ei[8]/Ei[6] + O[x]^terms, x] (* Jean-François Alcover, Mar 01 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 17 2017
STATUS
approved