a(n) = SF(2n-1)/SF(n-1)^2 where SF = A000178.A107254a(n) = SF(2n-1)/SF(n-1)^2 where SF = A000178.Terms a(0) =1a(1) =1a(2) =12a(3) =8640a(4) =870912000External referencesoeis: A107254