a(n) = Product_{k=0..n} ((4*k+1)*(4*k+3))^(n-k).A168440a(n) = Product_{k=0..n} ((4*k+1)*(4*k+3))^(n-k).Terms a(0) =1a(1) =3a(2) =315a(3) =3274425External referencesoeis: A168440