a(n) is the constant term in expansion of Product_{k=1..n} (x^(k^2) + 1 + 1/x^(k^2)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =3a(6) =7a(7) =19a(8) =43a(9) =95a(10) =189a(11) =429a(12) =1003a(13) =2457a(14) =6319a(15) =16165a(16) =41601a(17) =107969a(18) =280253a(19) =737065a(20) =1950865a(21) =5201941a(22) =13954313a(23) =37593679a(24) =101695957a(25) =276296549a(26) =753191093a(27) =2061201397a(28) =5658850121a(29) =15583938539