584064domain: NAppears in sequencesTheta series of direct sum of 2 copies of D_4 lattice in powers of q^2.at n=23A008658a(n) = product of numbers k <= sigma(n) such that k = sigma(d) for any divisor d of n where sigma = A000203.at n=44A206031a(n) = Product_{d|n} sigma(d) where sigma = A000203.at n=44A206032