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 A030599 #11 Dec 26 2018 11:54:12
%S A030599 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,1,1,1,1,1,1,1,
%T A030599 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,1,1,1,1,1,1,1,1,
%U A030599 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,1,1,1,1,1,1,1,1,1,1,1,1
%N A030599 Length of n-th run of digit 4 in A030588.
%H A030599 Antti Karttunen, <a href="/A030599/b030599.txt">Table of n, a(n) for n = 1..20000</a>
%o A030599 (PARI)
%o A030599 up_to = 20000;
%o A030599 A030599list(up_to,d=4) = { my(v=vector(up_to),ds=List([]),o=1,j=1,rl=0,i=0); while(i<up_to,if(j>#ds,ds=digits(o,6);j=1;o+=2); if(d==ds[j],rl++,if(rl,i++; v[i] = rl; rl=0)); j++); (v); };
%o A030599 v030599 = A030599list(up_to);
%o A030599 A030599(n) = v030599[n]; \\ _Antti Karttunen_, Dec 24 2018
%Y A030599 Cf. A030588, A030596, A030597, A030598, A030600.
%K A030599 nonn,base
%O A030599 1,25
%A A030599 _Clark Kimberling_
%E A030599 Terms corrected by _Antti Karttunen_, Dec 24 2018