a(n) = Product_{k=0..n} (3^k + 1).A323716a(n) = Product_{k=0..n} (3^k + 1).Terms a(0) =2a(1) =8a(2) =80a(3) =2240a(4) =183680a(5) =44817920a(6) =32717081600External referencesoeis: A323716