a(n) = Product_{i=1..n} (3^i - 1).A027871a(n) = Product_{i=1..n} (3^i - 1).Terms a(0) =1a(1) =2a(2) =16a(3) =416a(4) =33280a(5) =8053760a(6) =5863137280External referencesoeis: A027871