Expansion of g.f.: exp( Sum_{n>=1} 3^n*(Sum_{d|n} d*x^d)^n/n ).

Terms

a(0) =1a(1) =3a(2) =9a(3) =45a(4) =153a(5) =702a(6) =2754a(7) =11259a(8) =50058a(9) =224046a(10) =990873a(11) =4304988a(12) =18175185a(13) =77439321a(14) =327135510a(15) =1408297995a(16) =6302244447a(17) =29140976502a(18) =135628856406a(19) =622855827801