G.f. A(x) = Sum_{n=-oo..+oo} x^(n^2) * (2 - x^n)^n/(1 - 2*x^n)^n.

Terms

a(0) =1a(1) =4a(2) =6a(3) =12a(4) =32a(5) =48a(6) =120a(7) =192a(8) =450a(9) =784a(10) =1704a(11) =3072a(12) =6624a(13) =12288a(14) =25536a(15) =49404a(16) =100544a(17) =196608a(18) =398982a(19) =786432a(20) =1584192a(21) =3147924a(22) =6316032a(23) =12582912a(24) =25226304a(25) =50331712a(26) =100780032a(27) =201341856a(28) =402908016a(29) =805306368