a(n) = [x^(n^4)] 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) =2a(10) =3a(11) =9a(12) =20a(13) =43a(14) =85a(15) =183a(16) =394a(17) =1010a(18) =2254a(19) =5589a(20) =12383a(21) =31226a(22) =71153a(23) =182382a(24) =426055a(25) =1105686a(26) =2615167a(27) =6906858a(28) =16607500a(29) =44276140