a(n) = (1/4) * Sum_{k=0..floor(n/3)} (n-2*k+2) * 2^(n-2*k) * binomial(2*n-4*k+2,2*k+1).

A391834

a(n) = (1/4) * Sum_{k=0..floor(n/3)} (n-2*k+2) * 2^(n-2*k) * binomial(2*n-4*k+2,2*k+1).

Terms

    a(0) =1a(1) =6a(2) =24a(3) =86a(4) =320a(5) =1232a(6) =4696a(7) =17488a(8) =64160a(9) =233872a(10) =848960a(11) =3067200a(12) =11026672a(13) =39468576a(14) =140761344a(15) =500445344a(16) =1774199808a(17) =6273738240a(18) =22132498176a(19) =77912939008a(20) =273744796672a(21) =960083626496

External references