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 A071182 #2 Feb 11 2014 19:05:28
%S A071182 1,-1,3,-3,5,-5,1,-1,9,-9,11,-11,1,-1,15,-15,17,-17,1,-1,21,-21,3,-3,
%T A071182 1,-1,27,-27,29,-29,1,-1,3,-3,35,-35,1,-1,39,-39,41,-41,1,-1,45,-45,5,
%U A071182 -5,1,-1,51,-51,3,-3,1,-1,57,-57,59,-59,1,-1,3,-3,65,-65,1,-1,69,-69,71,-71,1,-1,5,-5,77,-77,1,-1,81,-81,3,-3,1
%N A071182 SPF(n+1)-SPF(n), where SPF(n) denotes the smallest prime factor of n.
%t A071182 g[n_] := (FactorInteger[n])[[1]][[1]]; f[n_] := g[n + 1] - g[n]; Table[f[i], {i, 2, 100}]
%K A071182 sign
%O A071182 2,3
%A A071182 _Joseph L. Pe_, Jun 10 2002