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

Terms

a(0) =1a(1) =1a(2) =3a(3) =8a(4) =15a(5) =34a(6) =67a(7) =133a(8) =255a(9) =486a(10) =901a(11) =1649a(12) =2984a(13) =5312a(14) =9373a(15) =16342a(16) =28221a(17) =48283a(18) =81928a(19) =137858a(20) =230278a(21) =381919a(22) =629156a(23) =1029933a(24) =1675856a(25) =2711288a(26) =4362575a(27) =6983196a(28) =11122327a(29) =17630798