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

A387929

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

Terms

    a(0) =1a(1) =5a(2) =39a(3) =344a(4) =3199a(5) =30645a(6) =299220a(7) =2960760a(8) =29585679a(9) =297877439a(10) =3017111599a(11) =30708223980a(12) =313808941636

External references