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 A064830 #9 Jun 19 2018 05:12:58
%S A064830 1,2,3,4,5,6,1,8,3,10,1,12,1,14,3,8,1,6,1,20,3,2,1,24,1,2,3,4,1,6,1,8,
%T A064830 3,2,5,12,1,2,3,8,1,42,1,4,9,2,1,48,1,10,3,4,1,18,1,8,3,2,1,60,1,2,63,
%U A064830 16,13,6,1,4,3,70,1,72,1,2,15,4,1,6,1,80,3,2,1,84,5,2,3,8,1,6,13,4,3,2
%N A064830 a(n) = gcd(n, prime(n)^2 - 1).
%H A064830 Harry J. Smith, <a href="/A064830/b064830.txt">Table of n, a(n) for n = 1..1000</a>
%e A064830 A000040(20) = 71, gcd(20, (71-1)*(71+1)) = 10 * gcd(2, 7*72) = 20 = a(20).
%t A064830 Table[ GCD[n, Prime[n]^2 - 1], {n, 1, 100} ]
%o A064830 (PARI) { for (n=1, 1000, write("b064830.txt", n, " ", gcd(n, prime(n)^2 - 1)) ) } \\ _Harry J. Smith_, Sep 27 2009
%Y A064830 Cf. A000040.
%K A064830 nonn
%O A064830 1,2
%A A064830 _Reinhard Zumkeller_, Oct 23 2001