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 A217976 #5 Oct 16 2012 14:26:13
%S A217976 1,2,4,9,21,62,159,422,1134,3056,8139,22169,60004,163262,443002
%N A217976 First time n appears in the first differences of n*log(n): A217865.
%C A217976 Conjecture: the last time n appears is always before the first time n+2 appears.
%C A217976 For example the last time 5 appears is at position 135, the first time 7 appears is at position 159.
%o A217976 (JavaScript)
%o A217976 function firstIndex(arr,k) {
%o A217976 p=-1;
%o A217976 for (a=1;a<arr.length;a++) if (arr[a]==k) {p=a;return p;}
%o A217976 return p;
%o A217976 }
%o A217976 d=new Array();
%o A217976 for (i=1; i<500000; i++)
%o A217976 d[i]=Math.floor((i+1)*Math.log(i+1))-Math.floor(i*Math.log(i));
%o A217976 for (i=1; i<100; i++) document.write(firstIndex(d, i)+", ");
%Y A217976 Cf. A217866.
%K A217976 nonn
%O A217976 1,2
%A A217976 _Jon Perry_, Oct 16 2012