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 A070221 #2 Feb 11 2014 19:05:28
%S A070221 1,-1,3,-2,4,-5,1,2,6,-8,10,-6,-2,-3,15,-14,16,-14,2,4,12,-20,2,8,-10,
%T A070221 4,22,-24,26,-29,9,6,-10,-4,34,-18,-6,-8,36,-34,36,-32,-6,18,24,-44,4,
%U A070221 -2,12,-4,40,-50,8,-4,12,10,30,-54,56,-30,-24,-5,11,-2,56,-50,6,-16,64,-68,70,-36,-32,14,-8,2,66,-74,-2,38,42,-76
%N A070221 a(n)=LPF(n+1)-LPF(n), where LPF(n) denotes the largest prime factor of n.
%e A070221 a(12) = LPF(13)-LPF(12) = 13 - 3 = 10.
%t A070221 g[n_] := Module[{a, b}, a = FactorInteger[n]; b = Length[a]; a[[b]][[1]]]; f[n_] := g[n + 1] - g[n]; Table[f[i], {i, 2, 100}]
%K A070221 sign
%O A070221 2,3
%A A070221 _Joseph L. Pe_, May 07 2002