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

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =13a(5) =23a(6) =39a(7) =63a(8) =101a(9) =159a(10) =243a(11) =367a(12) =547a(13) =801a(14) =1161a(15) =1665a(16) =2359a(17) =3315a(18) =4621a(19) =6385a(20) =8761a(21) =11941a(22) =16165a(23) =21757a(24) =29121a(25) =38761a(26) =51337a(27) =67673a(28) =88793a(29) =116009