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

Terms

a(0) =1a(1) =1a(2) =5a(3) =21a(4) =101a(5) =421a(6) =2021a(7) =8421a(8) =39397a(9) =167397a(10) =766437a(11) =3244517a(12) =14881253a(13) =62804453a(14) =283415013a(15) =1210159589a(16) =5401907685a(17) =22966866405a(18) =102497423845a(19) =435085808101