a(n) = Sum_{k=0..floor(n/2)} 2^(n-k) * binomial(k,n-2*k)^2.

Terms

a(0) =1a(1) =0a(2) =2a(3) =4a(4) =4a(5) =32a(6) =24a(7) =144a(8) =304a(9) =576a(10) =2336a(11) =3648a(12) =13120a(13) =30208a(14) =70528a(15) =218368a(16) =456448a(17) =1360896a(18) =3316224a(19) =8311808a(20) =23127040a(21) =54812672a(22) =151197696a(23) =380669952a(24) =978595840a(25) =2613067776a(26) =6540566528a(27) =17464705024a(28) =44764708864a(29) =116183662592