a(n) is the constant term in expansion of Product_{k=1..n} (x^(k^4) + 1 + 1/x^(k^4)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =1a(8) =1a(9) =3a(10) =3a(11) =15a(12) =25a(13) =59a(14) =109a(15) =227a(16) =525a(17) =1321a(18) =2917a(19) =7085a(20) =15893a(21) =38759a(22) =90179a(23) =223933a(24) =534867a(25) =1339691a(26) =3246961a(27) =8296441a(28) =20426971a(29) =52715563