Expansion of g.f.: 1/((1 - 2*x^2 + x^4 + 2*x^6 - x^8)*(1 - 2*x^2 - x^4 + 2*x^6 - x^8)).

Terms

a(0) =1a(1) =0a(2) =4a(3) =0a(4) =12a(5) =0a(6) =28a(7) =0a(8) =59a(9) =0a(10) =116a(11) =0a(12) =228a(13) =0a(14) =460a(15) =0a(16) =968a(17) =0a(18) =2092a(19) =0a(20) =4564a(21) =0a(22) =9908a(23) =0a(24) =21309a(25) =0a(26) =45444a(27) =0a(28) =96484a(29) =0