Sum ((-1)^(i+1)*binomial(n,i)*2^i*(2*n-1)!,i=1..n) for n odd.

A006523

Sum ((-1)^(i+1)*binomial(n,i)*2^i*(2*n-1)!,i=1..n) for n odd.

Terms

    a(0) =2a(1) =240a(2) =725760a(3) =12454041600

External references