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 A215088 #12 Mar 04 2014 00:47:50
%S A215088 0,1,2,3,4,2,3,4,5,6,4,5,6,7,8,6,7,8,9,10,8,9,10,11,12,4,5,6,7,8,6,7,
%T A215088 8,9,10,8,9,10,11,12,10,11,12,13,14,12,13,14,15,16,8,9,10,11,12,10,11,
%U A215088 12,13,14,12,13,14,15,16,14,15,16,17,18,16,17,18,19,20,12,13,14,15,16,14,15,16,17,18,16,17,18,19,20,18,19,20,21,22,20,21,22,23
%N A215088 a(n)=Sum{d(i)*2^i: i=0,1,...,m}, where Sum{d(i)*5^i: i=0,1,...,m} is the base 5 representation of n.
%H A215088 Clark Kimberling, <a href="/A215088/b215088.txt">Table of n, a(n) for n = 0..1000</a>
%F A215088 a(n) = 2*a(n/5) if n = 0 mod 5; otherwise, a(n) = a(n-1) + 1. - _Clark Kimberling_, Aug 03 2012
%t A215088 t = Table[FromDigits[RealDigits[n, 5], 2], {n, 0, 100}]
%Y A215088 Cf. A033042.
%K A215088 nonn,easy
%O A215088 0,3
%A A215088 _Clark Kimberling_, Aug 02 2012