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 A031013 #9 Feb 28 2014 01:21:58
%S A031013 5,17,31,45,59,64,66,68,70,72,73,74,76,87,106,127,148,169,190,197,200,
%T A031013 203,206,209,211,212,215,232,253,274,295,316,337,344,347,350,353,356,
%U A031013 358,359,362,379,400,421,442,463,484,491,494
%N A031013 Position of n-th 5 in A031007.
%H A031013 Vincenzo Librandi, <a href="/A031013/b031013.txt">Table of n, a(n) for n = 1..2000</a>
%t A031013 Flatten[Position[Flatten[Table[Reverse[IntegerDigits[n,7]],{n,0,200}]],5]]-1 (* _Harvey P. Dale_, Feb 25 2014 *)
%K A031013 nonn
%O A031013 1,1
%A A031013 _Clark Kimberling_