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

Terms

a(0) =1a(1) =2a(2) =4a(3) =18a(4) =34a(5) =166a(6) =544a(7) =2222a(8) =5396a(9) =29622a(10) =101276a(11) =411206a(12) =1170986a(13) =5435466a(14) =20007472a(15) =90854146a(16) =253956882a(17) =1160301990a(18) =4412414972a(19) =18080729238a(20) =56012061494a(21) =275783908498