a(n) = (1/n!)*Sum_{i=0..n-2} 4*(2*n+1)!*(2*n-i-4)!/(i!*(n-i-2)!*(2*n-i+1)).
A329776
a(n) = (1/n!)*Sum_{i=0..n-2} 4*(2*n+1)!*(2*n-i-4)!/(i!*(n-i-2)!*(2*n-i+1)).
Terms
- a(0) =0a(1) =48a(2) =1520a(3) =134640a(4) =24438960a(5) =7531426560
External references
- oeis: A329776