Expansion of Product_{k>=1} (1 + 3*x^k) / (1 - x^k).

Terms

a(0) =1a(1) =4a(2) =8a(3) =24a(4) =44a(5) =88a(6) =176a(7) =312a(8) =544a(9) =924a(10) =1584a(11) =2552a(12) =4136a(13) =6488a(14) =10128a(15) =15632a(16) =23748a(17) =35640a(18) =53080a(19) =78136a(20) =114024a(21) =165552a(22) =237744a(23) =339544a(24) =481248a(25) =678236a(26) =949008a(27) =1321840a(28) =1830376a(29) =2521688