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 A051815 #4 Jun 11 2014 17:24:22
%S A051815 1,12,105,780,5452,39979,336081,3263355,34518027,372779338,3957184040,
%T A051815 40729856248,406862880846,3979167973684,38556471560342,374259579575061
%N A051815 Number of n-digit numbers with nonzero multiplicative digital root 4.
%D A051815 William Mayne, sci.math, Jun 15 1991
%F A051815 # { i : 10^(n-1) < i < 10^n and A051802(i)=4 }
%Y A051815 Cf. A051802, A051806, A051824.
%K A051815 nonn,base,hard
%O A051815 1,2
%A A051815 _Dan Hoey_, Dec 09 1999