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

Terms

a(0) =0a(1) =1a(2) =4a(3) =14a(4) =46a(5) =147a(6) =462a(7) =1437a(8) =4438a(9) =13637a(10) =41746a(11) =127426a(12) =388076a(13) =1179739a(14) =3581052a(15) =10856790a(16) =32880942a(17) =99496293a(18) =300845658a(19) =909073356a(20) =2745419352a(21) =8287110075a(22) =25003877784a(23) =75412396575a(24) =227366950140a(25) =685293578217