Regarding computing an eta product

["LNU, Swati" <S10@email.sc.edu>]

Hello all,

Is it possible to modify the function 

q^(a) * (eta (Mod(1, m) * q + O(q^(n + 1))))^(24 * a), 

which computes the series expansion of various powers of Ramanujan Delta function and reduces coefficients modulo m, to compute the expansion of various powers of 

the following eta product and reduce coefficients mod m:

(\eta(z) \eta(3z) \eta(5z) \eta(15 z))^(a).

I tried changing q -> q^(ka) and flag to a non-zero value for the individual products, but it does not seem to work. Here, k \in {1, 3, 5, 15 \} and a is any positive integer.

I would appreciate any suggestions in this regard.

Thanks,

Swati