a(n) = n! * Sum_{ 0<=i<=j<=k<=n, i+j+k<=n } 1/(i!*j!*k!).
A076177
a(n) = n! * Sum_{ 0<=i<=j<=k<=n, i+j+k<=n } 1/(i!*j!*k!).
Terms
- a(0) =1a(1) =2a(2) =7a(3) =31a(4) =147a(5) =801a(6) =5028a(7) =35757a(8) =287703a(9) =2594737a(10) =25961688a(11) =285620919a(12) =3427588046a(13) =44559016789a(14) =623827340321
External references
- oeis: A076177