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 A095900 #12 Oct 05 2017 04:03:25
%S A095900 1,6,57,510,5373,53505,510403,5247173,52736107,511172800,5189628970,
%T A095900 52334438874,511861449132,5150236044255,52074775905991,
%U A095900 512279427101305,5118687220533539,51879201305335167,512519244788358058
%N A095900 a(n) = A004001(10^n).
%C A095900 a(n)/n -> 10^n/(2*n). [Corrected by Herman Jamke (hermanjamke(AT)fastmail.fm), Apr 28 2007]
%H A095900 Herman Jamke, <a href="/A095900/b095900.txt">Table of n, a(n) for n = 0..30</a>
%H A095900 C. L. Mallows, <a href="http://www.jstor.org/stable/2324028">Conway's challenge sequence</a>, Amer. Math. Monthly, 98 (1991), 5-20. See comments on formula due to G. Phillips on page 18.
%t A095900 a[1] = a[2] = 1; a[n_] := a[n] = a[a[n - 1]] + a[n - a[n - 1]]; Do[ a[n], {n, 1000000}]; Table[ a[10^n], {n, 0, 6}]
%o A095900 (PARI) print1("1, ");for(k=1,30,n=10^k;row=floor(log(n)/log(2));col=1;s=0;a=0;while(s<n,for(j=col,row+1,if(j>1,smd=binomial(row,j-2),smd=2^row);if((s+smd)>n,col=j-1;row=row-1;break,s+=smd;if(j>1,a+=binomial(row-1,j-2),a+=2^(row-1)))));print1(a", ")) \\ Herman Jamke (hermanjamke(AT)fastmail.fm), Apr 28 2007
%Y A095900 Cf. A004001.
%K A095900 nonn
%O A095900 0,2
%A A095900 _Robert G. Wilson v_, Jun 11 2004
%E A095900 2 more terms from _Ryan Propper_, Jan 05 2007
%E A095900 More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Apr 28 2007