G.f.: Product_{k>=1} 1/(1-x^k)^(2*k-1).

Terms

a(0) =1a(1) =1a(2) =4a(3) =9a(4) =22a(5) =46a(6) =103a(7) =208a(8) =431a(9) =849a(10) =1671a(11) =3195a(12) =6079a(13) =11321a(14) =20937a(15) =38146a(16) =68931a(17) =123121a(18) =218212a(19) =383019a(20) =667425a(21) =1153544a(22) =1980268a(23) =3375394a(24) =5717773a(25) =9624541a(26) =16108496a(27) =26807662a(28) =44379189a(29) =73089219