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

Terms

a(0) =1a(1) =3a(2) =4a(3) =7a(4) =13a(5) =23a(6) =33a(7) =51a(8) =74a(9) =110a(10) =158a(11) =222a(12) =307a(13) =429a(14) =587a(15) =792a(16) =1065a(17) =1423a(18) =1877a(19) =2470a(20) =3227a(21) =4196a(22) =5416a(23) =6963a(24) =8899a(25) =11344a(26) =14384a(27) =18158a(28) =22840a(29) =28647