a(n) = 2^(n-1) + ((1+(-1)^n)/4)*binomial(n, n/2) - binomial(n, floor(n/2)).

Terms

a(0) =0a(1) =0a(2) =1a(3) =1a(4) =5a(5) =6a(6) =22a(7) =29a(8) =93a(9) =130a(10) =386a(11) =562a(12) =1586a(13) =2380a(14) =6476a(15) =9949a(16) =26333a(17) =41226a(18) =106762a(19) =169766a(20) =431910a(21) =695860a(22) =1744436a(23) =2842226a(24) =7036530a(25) =11576916a(26) =28354132a(27) =47050564a(28) =114159428a(29) =190876696