a(n) = Product_{k=1..n-1} (4^k + 1).A309327a(n) = Product_{k=1..n-1} (4^k + 1).Terms a(0) =1a(1) =1a(2) =5a(3) =85a(4) =5525a(5) =1419925a(6) =1455423125External referencesoeis: A309327