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

A378406

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

Terms

    a(0) =1a(1) =1a(2) =3a(3) =16a(4) =67a(5) =266a(6) =1116a(7) =4803a(8) =20707a(9) =89665a(10) =390868a(11) =1712283a(12) =7527664a(13) =33196606a(14) =146800811a(15) =650724896a(16) =2890442051a(17) =12862496583a(18) =57331583055a(19) =255915024714

External references