G.f.: exp( Sum_{n>=1} 3^b(n) * x^n/n ) where b(n) = highest exponent of 3 in 2^n+1.

Terms

a(0) =1a(1) =3a(2) =5a(3) =9a(4) =15a(5) =21a(6) =29a(7) =39a(8) =49a(9) =63a(10) =81a(11) =99a(12) =123a(13) =153a(14) =183a(15) =219a(16) =261a(17) =303a(18) =353a(19) =411a(20) =469a(21) =537a(22) =615a(23) =693a(24) =781a(25) =879a(26) =977a(27) =1089a(28) =1215a(29) =1341