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

Terms

a(0) =1a(1) =1a(2) =4a(3) =8a(4) =13a(5) =20a(6) =32a(7) =52a(8) =84a(9) =133a(10) =204a(11) =304a(12) =444a(13) =636a(14) =900a(15) =1264a(16) =1761a(17) =2440a(18) =3364a(19) =4608a(20) =6276a(21) =8496a(22) =11424a(23) =15268a(24) =20284a(25) =26789a(26) =35196a(27) =46016a(28) =59884a(29) =77612