a(n) = Sum_{1<=i<=j<=k<=n} (i+j+k)!/(i!*j!*k!).
A307353
a(n) = Sum_{1<=i<=j<=k<=n} (i+j+k)!/(i!*j!*k!).
Terms
- a(0) =0a(1) =6a(2) =138a(3) =2808a(4) =59083a(5) =1298797a(6) =29538183a(7) =688783509a(8) =16365391557a(9) =394523905488
External references
- oeis: A307353