E.g.f.: A(x) = exp( Sum_{n>=0} x^(3^n)/3^((3^n -1)/2) ).

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =9a(5) =21a(6) =81a(7) =351a(8) =1233a(9) =10249a(10) =75841a(11) =388411a(12) =3733401a(13) =33702813a(14) =215375889a(15) =1984583511a(16) =19181083041a(17) =141963117201