This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A051821 #4 Jun 11 2014 17:24:23
%S A051821 1,6,30,273,3321,38545,413435,4179623,40717550,389610397,3704647927,
%T A051821 35103992478,330893886987,3100780107689,28983549003377,272016949455533
%N A051821 Number of numbers below 10^n with nonzero multiplicative digital root 1 (not counting 0).
%D A051821 William Mayne, sci.math, Jun 15 1991
%F A051821 # { i : 10^(n-1) < i < 10^n and A051802(i)=1 }
%Y A051821 Cf. A051802, A051803, A051812.
%K A051821 nonn,base,hard
%O A051821 1,2
%A A051821 _Dan Hoey_, Dec 09 1999