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 A071582 #10 Apr 09 2015 11:12:56
%S A071582 1,4,61,46,652,4201,6904,48361,63556,441262,6758401,4034914,61277761,
%T A071582 46880176,654534862,4281473701,6927694924,48196897171,63767491786,
%U A071582 449609778472,6777261159901,4011156408934,61444068129571
%N A071582 Powers of 4 written backwards.
%H A071582 Alois P. Heinz, <a href="/A071582/b071582.txt">Table of n, a(n) for n = 0..1000</a>
%p A071582 a:= n-> (s-> parse(cat(s[-i]$i=1..length(s))))(""||(4^n)):
%p A071582 seq(a(n), n=0..50); # _Alois P. Heinz_, Apr 09 2015
%t A071582 FromDigits[Reverse[IntegerDigits[#]]]&/@(4^Range[0,30]) (* _Harvey P. Dale_, Jan 28 2013 *)
%o A071582 (PARI) for(i=1,50,n=4^i; s=ceil(log(n)/log(10)); print1(sum(i=0,s,10^(s-i-1)*(floor(n/10^i)-10*floor(n/10^(i+1)))),","))
%K A071582 easy,nonn,base
%O A071582 0,2
%A A071582 _Benoit Cloitre_, Jun 01 2002