Expansion of Product_{k>=1} (1 + 4*x^k)/(1 - 4*x^k).

Terms

a(0) =1a(1) =8a(2) =40a(3) =200a(4) =872a(5) =3720a(6) =15400a(7) =62920a(8) =254440a(9) =1024648a(10) =4112680a(11) =16483400a(12) =66000360a(13) =264150920a(14) =1056903080a(15) =4228272200a(16) =16914393832a(17) =67660396040a(18) =270647139240