a(n) = v(n+1)/(2*v(n)), where v = A203305.

A203307

a(n) = v(n+1)/(2*v(n)), where v = A203305.

Terms

    a(0) =1a(1) =12a(2) =672a(3) =161280a(4) =159989760a(5) =645078712320

External references