a(n) = Product_{k=0..n} (4^k + 4^(n-k)).A369675a(n) = Product_{k=0..n} (4^k + 4^(n-k)).Terms a(0) =2a(1) =25a(2) =2312a(3) =1690000a(4) =9773138432External referencesoeis: A369675