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

Terms

a(0) =1a(1) =1a(2) =3a(3) =12a(4) =36a(5) =135a(6) =432a(7) =1539a(8) =4860a(9) =17496a(10) =55404a(11) =192456a(12) =623295a(13) =2125764a(14) =6849684a(15) =23442453a(16) =75110328a(17) =252965916a(18) =822670668a(19) =2735858268a(20) =8838926712a(21) =29501352792a(22) =95090206689a(23) =314068876416