Expansion of g.f.: Product_{n>=1} 1/(1 - 3^n*x^n)^(3/3^n).

Terms

a(0) =1a(1) =3a(2) =12a(3) =39a(4) =138a(5) =426a(6) =1461a(7) =4458a(8) =14655a(9) =45309a(10) =145479a(11) =443037a(12) =1427196a(13) =4329696a(14) =13655325a(15) =41795679a(16) =131102229a(17) =397649811a(18) =1247247507a(19) =3775785681a(20) =11761535064a(21) =35770717695a(22) =110693177805a(23) =335003030301