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 A018866 #10 Feb 22 2018 19:06:16
%S A018866 0,4,3,2,8,14,1,7,13,45,6,38,12,57,31,5,50,37,11,69,43,30,17,4,49,36,
%T A018866 23,10,68,55,42,29,16,3,61,48,35,106,22,9,67,138,54,41,28,99,15,228,2,
%U A018866 60,131,47,260,34,21,92,8,150,66,137,53,195,40,182,27,98,14,85,298,72,285
%N A018866 7^a(n) is smallest power of 7 beginning with n.
%H A018866 D. Mondot, <a href="/A018866/b018866.txt">Table of n, a(n) for n=1..32699</a>
%t A018866 With[{s=7^Range[0,500]},Flatten[Table[Position[s,_?(IntegerDigits[n] == Take[IntegerDigits[#],IntegerLength[n]]&),1,1],{n,80}]]]-1//Quiet (* _Harvey P. Dale_, Feb 22 2018 *)
%K A018866 nonn,base
%O A018866 1,2
%A A018866 _David W. Wilson_