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

Terms

a(0) =1a(1) =4a(2) =4a(3) =20a(4) =20a(5) =36a(6) =100a(7) =116a(8) =180a(9) =260a(10) =580a(11) =660a(12) =1044a(13) =1380a(14) =2020a(15) =3444a(16) =4340a(17) =6020a(18) =8260a(19) =11220a(20) =14740a(21) =23140a(22) =28196a(23) =38900a(24) =50420a(25) =67780a(26) =85956a(27) =114900a(28) =157140a(29) =197860