a(n) = -Sum_{i=1..n} Sum_{j=1..n} Sum_{k=1..n} (-1)^(i+j+k) * (i+j+k)!/(3!*i!*j!*k!).
A307350
a(n) = -Sum_{i=1..n} Sum_{j=1..n} Sum_{k=1..n} (-1)^(i+j+k) * (i+j+k)!/(3!*i!*j!*k!).
Terms
- a(0) =0a(1) =1a(2) =-5a(3) =120a(4) =-2380a(5) =52556a(6) =-1192625a(7) =27798310a(8) =-660128942a(9) =15907062666a(10) =-387785597485
External references
- oeis: A307350