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 A195212 #17 Jul 22 2013 16:27:45 %S A195212 4,9,16,18,25,36,49,50,64,72,75,81,98,100,121,144,147,150,162,169,196, %T A195212 200,225,242,245,256,288,289,294,300,324,338,361,363,392,400,441,450, %U A195212 484,490,507,529,576,578,588,600,605,625,648,675,676,722,726,729,735 %N A195212 Numbers n for which the exponent of the largest prime factor of n is even. %C A195212 What is the density of these numbers? It's clear that lim a(n)/n^2 = 0. %H A195212 Charles R Greathouse IV, <a href="/A195212/b195212.txt">Table of n, a(n) for n = 1..10000</a> %t A195212 Select[Range[800],EvenQ[FactorInteger[#][[-1,2]]]&] (* _Harvey P. Dale_, Jul 22 2013 *) %o A195212 (PARI) is(n)=if(n<4,0,n=factor(n)[,2];n[#n]%2==0) \\ _Charles R Greathouse IV_, Sep 14 2011 %Y A195212 Contains the squares, A000290, as a subsequence (apart from 0 and 1). %K A195212 nonn %O A195212 1,1 %A A195212 _Charles R Greathouse IV_, Sep 13 2011