Revert transform of (-1 + x + x^2)/((x - 1)*(x + 1)).

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =20a(5) =71a(6) =264a(7) =1015a(8) =4002a(9) =16094a(10) =65758a(11) =272208a(12) =1139182a(13) =4811807a(14) =20487096a(15) =87832558a(16) =378846620a(17) =1642851797a(18) =7158220968a(19) =31323340342a(20) =137595355130a(21) =606533278416