a(n) = Sum_{k=0..n} 3^(n-k) * binomial(n,k) * binomial(2*n+1,k).
A388133
a(n) = Sum_{k=0..n} 3^(n-k) * binomial(n,k) * binomial(2*n+1,k).
Terms
- a(0) =1a(1) =6a(2) =49a(3) =440a(4) =4131a(5) =39810a(6) =390300a(7) =3873504a(8) =38794135a(9) =391287386a(10) =3968936049a(11) =40443812744a(12) =413708253076
External references
- oeis: A388133