L.g.f.: log( Product_{n>=1} 1/(1 - (2^n+1)*x^n) ).

Terms

a(0) =0a(1) =3a(2) =19a(3) =54a(4) =199a(5) =408a(6) =1612a(7) =3090a(8) =11023a(9) =26487a(10) =80994a(11) =199686a(12) =676540a(13) =1700832a(14) =5285096a(15) =15197274a(16) =45739039a(17) =131368404a(18) =401655943a(19) =1172222958a(20) =3549402474a(21) =10533769146a(22) =31617172980a(23) =94336116834a(24) =283990486780a(25) =848323147233