|
|
A145723
|
|
Expansion of q^(-1) * f(q) * chi(-q^5) / f(-q^20) in powers of q where f(), chi() are Ramanujan theta functions.
|
|
4
|
|
|
1, 1, -1, 0, 0, -2, -1, 0, 0, 0, 1, 0, 0, 0, 0, 0, -1, 2, 0, 0, 2, 2, 0, 0, 0, -4, -1, 0, 0, 0, 2, 0, -1, 0, 0, 0, -2, 2, 0, 0, 3, 4, -2, 0, 0, -8, -3, 0, 0, 0, 5, 0, -2, 0, 0, 0, -3, 4, 0, 0, 6, 8, -2, 0, 0, -14, -4, 0, 0, 0, 8, 0, -3, 0, 0, 0, -6, 8, 0, 0
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
-1,6
|
|
COMMENTS
|
|
|
LINKS
|
|
|
FORMULA
|
Expansion of eta(q^2)^3 * eta(q^5) / (eta(q) * eta(q^4) * eta(q^10) * eta(q^20)) in powers of q.
Euler transform of period 20 sequence [ 1, -2, 1, -1, 0, -2, 1, -1, 1, -2, 1, -1, 1, -2, 0, -1, 1, -2, 1, 0, ...].
G.f. is a period 1 Fourier series which satisfies f(-1 / (80 t)) = 20^(1/2) g(t) where q = exp(2 Pi i t) and g() is the g.f. for A145722.
a(4*n + 2) = a(5*n + 2) = a(5*n + 3) = 0.
|
|
EXAMPLE
|
G.f. = 1/q + 1 - q - 2*q^4 - q^5 + q^9 - q^15 + 2*q^16 + 2*q^19 + 2*q^20 + ...
|
|
MATHEMATICA
|
a[ n_] := SeriesCoefficient[ 1/q QPochhammer[ -q] QPochhammer[ q^5, q^10] / QPochhammer[ q^20], {q, 0, n}]; (* Michael Somos, Sep 05 2015 *)
|
|
PROG
|
(PARI) {a(n) = my(A); if( n<-1, 0, n++; A = x * O(x^n); polcoeff( eta(x^2 + A)^3 * eta(x^5 + A) / (eta(x + A) * eta(x^4 + A) * eta(x^10 + A) * eta(x^20 + A)), n))};
|
|
CROSSREFS
|
|
|
KEYWORD
|
sign
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|