|
| |
|
|
A128711
|
|
Expansion of phi(x) * psi(x^4) * phi(-x^4)^4 in powers of x where phi(), psi() are Ramanujan theta functions.
|
|
3
|
|
|
|
1, 2, 0, 0, -5, -14, 0, 0, 2, 34, 0, 0, 25, -28, 0, 0, -28, 0, 0, 0, -46, -14, 0, 0, 49, 4, 0, 0, 68, 82, 0, 0, 0, -62, 0, 0, -142, 50, 0, 0, -11, -158, 0, 0, 146, 0, 0, 0, -94, 70, 0, 0, 0, 178, 0, 0, 98, 0, 0, 0, 75, -92, 0, 0, -28, -62, 0, 0, -238, -206, 0
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
0,2
|
|
|
COMMENTS
|
Number 48 of the 74 eta-quotients listed in Table I of Martin (1996).
|
|
|
LINKS
|
|
|
|
FORMULA
|
Expansion of q^(-1/2) * (eta(q^2) * eta(q^4))^5 / (eta(q) * eta(q^8))^2 in powers of q. - Michael Somos, Mar 14 2012
Euler transform of period 8 sequence [ 2, -3, 2, -8, 2, -3, 2, -6, ...].
a(n) = b(2*n + 1) where b() is multiplicative with b(2^e) = 0^e, b(p^e) = (1 + (-1)^e)/2 * p^e if p == 5, 7 (mod 8), b(p^e) = b(p) * b(p^(e-1)) - p^2 * b(p^(e-2)) if p == 1, 3 (mod 8) where b(p) = 2*(2*x^2 - p) * (-1)^((p-1)/2) and p = x^2 + 2*y^2.
G.f. is a period 1 Fourier series which satisfies f(-1 / (32 t)) = 2^(15/2) (t/i)^3 f(t) where q = exp(2 Pi i t).
G.f.: Product_{k>0} (1 - x^k)^6 * (1 + x^k)^8 * (1 + x^(2*k))^3 / (1 + x^(4*k))^2.
a(4*n + 2) = a(4*n + 3) = 0. a(4*n) = A128712(n). a(4*n + 1) = 2 * A128713(n).
|
|
|
EXAMPLE
|
G.f. = 1 + 2*x - 5*x^4 - 14*x^5 + 2*x^8 + 34*x^9 + 25*x^12 - 28*x^13 + ...
G.f. = q + 2*q^3 - 5*q^9 - 14*q^11 + 2*q^17 + 34*q^19 + 25*q^25 - 28*q^27 + ...
|
|
|
MATHEMATICA
|
a[ n_] := SeriesCoefficient[ (QPochhammer[ x^2] QPochhammer[ x^4])^5 / (QPochhammer[ x] QPochhammer[ x^8])^2, {x, 0, n}]; (* Michael Somos, Jul 09 2015 *)
|
|
|
PROG
|
(PARI) {a(n) = my(A, p, e, x, y, a0, a1); if( n<0, 0, n = 2*n + 1; A = factor(n); prod( k=1, matsize(A)[1], [p, e] = A[k, ]; if( p==2, 0, p%8>4, if( e%2, 0, p^e), for( i=1, sqrtint(p\2), if( issquare(p - 2*i^2, &x), break)); a0=1; a1=y=2*(2*x^2 - p) * (-1)^((p-1)/2); for( i=2, e, x = y*a1 - p^2*a0; a0=a1; a1=x); a1)))};
(PARI) {a(n) = my(A); if( n<0, 0, A = x * O(x^n); polcoeff( (eta(x^2 + A) * eta(x^4 + A))^5 / (eta(x + A) * eta(x^8 + A))^2, n))};
|
|
|
CROSSREFS
|
|
|
|
KEYWORD
|
sign
|
|
|
AUTHOR
|
|
|
|
STATUS
|
approved
|
| |
|
|
