Number of compositions of n with an even number of 1's.

Terms

a(0) =1a(1) =0a(2) =2a(3) =1a(4) =6a(5) =6a(6) =20a(7) =28a(8) =72a(9) =120a(10) =272a(11) =496a(12) =1056a(13) =2016a(14) =4160a(15) =8128a(16) =16512a(17) =32640a(18) =65792a(19) =130816a(20) =262656a(21) =523776a(22) =1049600a(23) =2096128a(24) =4196352a(25) =8386560a(26) =16781312a(27) =33550336a(28) =67117056a(29) =134209536