OFFSET
19,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 19..10000
H. Gupta, On the coefficients of the powers of Dedekind's modular form, J. London Math. Soc., 39 (1964), 433-440.
H. Gupta, On the coefficients of the powers of Dedekind's modular form (annotated and scanned copy)
FORMULA
a(n) = [x^n]( QPochhammer(-x) - 1 )^19. - G. C. Greubel, Sep 07 2023
MAPLE
g:= proc(n) option remember; `if`(n=0, 1, add(add([-d, d, -2*d, d]
[1+irem(d, 4)], d=numtheory[divisors](j))*g(n-j), j=1..n)/n)
end:
b:= proc(n, k) option remember; `if`(k=0, 1, `if`(k=1, `if`(n=0, 0, g(n)),
(q-> add(b(j, q)*b(n-j, k-q), j=0..n))(iquo(k, 2))))
end:
a:= n-> b(n, 19):
seq(a(n), n=19..46); # Alois P. Heinz, Feb 07 2021
MATHEMATICA
nmax=46; CoefficientList[Series[(Product[(1-(-x)^j), {j, nmax}] - 1)^19, {x, 0, nmax}], x]//Drop[#, 19] & (* Ilya Gutkovskiy, Feb 07 2021 *)
With[{k=19}, Drop[CoefficientList[Series[(QPochhammer[-x] -1)^k, {x, 0, 75}], x], k]] (* G. C. Greubel, Sep 07 2023 *)
PROG
(Magma)
m:=80;
R<x>:=PowerSeriesRing(Integers(), m);
Coefficients(R!( ((&*[1-(-x)^j: j in [1..m+2]]) -1)^(19) )); // G. C. Greubel, Sep 07 2023
(SageMath)
from sage.modular.etaproducts import qexp_eta
m=75; k=19;
def f(k, x): return (-1 + qexp_eta(QQ[['q']], m+2).subs(q=-x) )^k
def A047644_list(prec):
P.<x> = PowerSeriesRing(QQ, prec)
return P( f(k, x) ).list()
a=A047644_list(m); a[k:] # G. C. Greubel, Sep 07 2023
(PARI) my(x='x+O('x^35)); Vec((eta(-x)-1)^19) \\ Joerg Arndt, Sep 07 2023
CROSSREFS
KEYWORD
sign
AUTHOR
EXTENSIONS
Definition and offset edited by Ilya Gutkovskiy, Feb 07 2021
STATUS
approved