G.f.: Sum_{n=-oo..+oo} (1 + x^n)^n / (1 - x^n)^n, ignoring the constant term.

Terms

a(0) =4a(1) =0a(2) =16a(3) =16a(4) =24a(5) =0a(6) =32a(7) =96a(8) =116a(9) =0a(10) =48a(11) =192a(12) =56a(13) =0a(14) =608a(15) =704a(16) =72a(17) =0a(18) =80a(19) =480a(20) =1408a(21) =0a(22) =96a(23) =3712a(24) =2108a(25) =0a(26) =2720a(27) =896a(28) =120a(29) =0