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 A037475 #9 Aug 03 2014 14:27:16
%S A037475 0,1,2,3,4,5,6,9,10,11,12,13,14,15,18,19,20,21,22,23,24,27,28,29,30,
%T A037475 31,32,33,36,37,38,39,40,41,42,45,46,47,48,49,50,51,54,55,56,57,58,59,
%U A037475 60,81,82,83,84,85,86,87,90,91,92,93,94,95,96,99,100,101,102
%N A037475 a(n)=Sum{d(i)*9^i: i=0,1,...,m}, where Sum{d(i)*7^i: i=0,1,...,m} is the base 7 representation of n.
%H A037475 Clark Kimberling, <a href="/A037475/b037475.txt">Table of n, a(n) for n = 0..1000</a>
%t A037475 Table[FromDigits[RealDigits[n, 7], 9], {n, 0, 100}]
%t A037475 (* _Clark Kimberling_, Aug 14 2012 *)
%K A037475 nonn,base
%O A037475 0,3
%A A037475 _Clark Kimberling_
%E A037475 Offset changed to 0 by _Clark Kimberling_, Aug 14 2012