Expansion of g.f. A(x) = Sum_{n=-oo..+oo} x^n * (2 + x^n)^(2*n).

Terms

a(0) =1a(1) =5a(2) =16a(3) =77a(4) =256a(5) =1104a(6) =4121a(7) =16832a(8) =65536a(9) =264688a(10) =1048617a(11) =4205568a(12) =16779008a(13) =67162112a(14) =268436016a(15) =1073999165a(16) =4294967296a(17) =17180983296a(18) =68719549696a(19) =274882887680