theta3(z) * theta3(2*z) * theta3(3*z) * theta3(6*z).

Terms

a(0) =1a(1) =2a(2) =2a(3) =6a(4) =6a(5) =4a(6) =14a(7) =8a(8) =6a(9) =26a(10) =12a(11) =16a(12) =42a(13) =12a(14) =16a(15) =44a(16) =6a(17) =20a(18) =50a(19) =16a(20) =36a(21) =56a(22) =24a(23) =16a(24) =42a(25) =30a(26) =28a(27) =78a(28) =48a(29) =36