OFFSET
0,2
COMMENTS
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
D. Alexander, C. Cummins, J. McKay and C. Simons, Completely Replicable Functions, LMS Lecture Notes, 165, ed. Liebeck and Saxl (1992), 87-98, annotated and scanned copy.
D. Ford, J. McKay and S. P. Norton, More on replicable functions, Commun. Algebra 22, No. 13, 5175-5193 (1994).
Michael Somos, Introduction to Ramanujan theta functions
Eric Weisstein's World of Mathematics, Ramanujan Theta Functions
FORMULA
Expansion of a(x) / (psi(x) * psi(x^3)) in powers of x where psi() is a Ramanujan theta function and a() is a cubic AGM theta function. - Michael Somos, Aug 20 2012
Expansion of q^(1/2) * (eta(q)^3 + 9 * q * eta(q^9)^3) * eta(q) / (eta(q^2) * eta(q^6))^2 in powers of q. - Michael Somos, Aug 20 2012
EXAMPLE
G.f. = 1 + 5*x - 5*x^2 + 9*x^3 - 14*x^4 + 19*x^5 - 34*x^6 + 55*x^7 - 69*x^8 + ...
T12c = 1/q + 5*q - 5*q^3 + 9*q^5 - 14*q^7 + 19*q^9 - 34*q^11 + 55*q^13 - ...
MATHEMATICA
a[n_]:= SeriesCoefficient[(QPochhammer[x]^3 + 9*x*QPochhammer[x^9]^3)* QPochhammer[x]/(QPochhammer[x^2]*QPochhammer[x^6])^2, {x, 0, n}]; (* Michael Somos, Sep 14 2015 *)
PROG
(PARI) {a(n) = my(A); if( n<0, 0, A = x * O(x^n); polcoeff( (eta(x + A)^3 + 9 * x * eta(x^9 + A)^3) * eta(x + A) / (eta(x^2 + A) * eta(x^6 + A))^2, n))}; /* Michael Somos, Aug 20 2012 */
(PARI) { my(q='q+O('q^66)); Vec( (eta(q)^3 + 9 * q * eta(q^9)^3) * eta(q) / (eta(q^2) * eta(q^6))^2 ) } \\ Joerg Arndt, Apr 16 2017
CROSSREFS
KEYWORD
sign
AUTHOR
N. J. A. Sloane, Nov 27 2000
EXTENSIONS
Name changed by N. J. A. Sloane, Jun 10 2015 at the suggestion of Yang-Hui He
STATUS
approved