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

Terms

a(0) =1a(1) =5a(2) =33a(3) =233a(4) =1697a(5) =12585a(6) =94449a(7) =714873a(8) =5445441a(9) =41687369a(10) =320420753a(11) =2471008281a(12) =19108837601a(13) =148123058153