Hello SeqFans, you'll get S, I guess, multiplying a(n) by the n-th digit of S: S = 2,4,16,16,96,96,576,5184,31104,279936,1679616,8398080,58786560,... (if you have to multiply by zero, multiply by 10 instead) (starting S with 1 gives http://oeis.org/A000012) Best, É.