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 A031003 #6 May 06 2014 15:30:51 %S A031003 4,16,30,44,49,51,53,55,57,58,59,61,72,86,105,126,147,168,176,179,182, %T A031003 185,188,189,191,194,210,231,252,273,294,315,323,326,329,332,335,336, %U A031003 338,341,357,378,399,420,441,462,470,473,476 %N A031003 Position of n-th 4 in A030998. %t A031003 Flatten[Position[Flatten[IntegerDigits[#,7]&/@Range[0,200]],4]]-1 (* _Harvey P. Dale_, May 06 2014 *) %K A031003 nonn %O A031003 1,1 %A A031003 _Clark Kimberling_