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

A379085

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

Terms

    a(0) =1a(1) =2a(2) =6a(3) =26a(4) =142a(5) =802a(6) =4434a(7) =24222a(8) =132686a(9) =733076a(10) =4081926a(11) =22853052a(12) =128427106a(13) =723862856a(14) =4090573570a(15) =23170106086a(16) =131515806574a(17) =747875338152

External references