a(n) = Sum_{k=0..n} (k+2) * binomial(3*n-2*k+2,n-k)/(3*n-2*k+2).
A390719
a(n) = Sum_{k=0..n} (k+2) * binomial(3*n-2*k+2,n-k)/(3*n-2*k+2).
Terms
- a(0) =1a(1) =3a(2) =11a(3) =47a(4) =222a(5) =1121a(6) =5930a(7) =32451a(8) =182207a(9) =1043858a(10) =6077706a(11) =35859253a(12) =213932707a(13) =1288352838a(14) =7821620103a(15) =47818928943a(16) =294148895958
External references
- oeis: A390719