G.f.: Sum_{k>=0} x^(k*(k+1)/2) / Product_{j=1..k} (1 - x^(2*j-1))^2.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =6a(5) =8a(6) =13a(7) =18a(8) =23a(9) =33a(10) =44a(11) =57a(12) =77a(13) =99a(14) =125a(15) =163a(16) =207a(17) =259a(18) =328a(19) =407a(20) =503a(21) =626a(22) =769a(23) =938a(24) =1149a(25) =1397a(26) =1687a(27) =2044a(28) =2458a(29) =2943