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

A389153

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

Terms

    a(0) =1a(1) =1a(2) =3a(3) =19a(4) =91a(5) =391a(6) =1767a(7) =8331a(8) =39411a(9) =186427a(10) =887113a(11) =4246265a(12) =20400931a(13) =98295211a(14) =474876377a(15) =2299723429a(16) =11160126595a(17) =54255979843a(18) =264196953489

External references