a(n) = Sum_{0<=i<=j<=k<=n} (-1)^(i+j+k) * (i+j+k)!/(i!*j!*k!).

A307358

a(n) = Sum_{0<=i<=j<=k<=n} (-1)^(i+j+k) * (i+j+k)!/(i!*j!*k!).

Terms

    a(0) =1a(1) =-4a(2) =72a(3) =-1345a(4) =27886a(5) =-610558a(6) =13861334a(7) =-322838475a(8) =7663363513a(9) =-184598740512

External references