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 A219028 #23 Aug 19 2016 00:28:26
%S A219028 0,1,2,4,6,8,8,12,12,16,22,24,24,30,24,28,30,44,46,46,48,54,42,48,64,
%T A219028 60,70,54,72,64,90,82,72,94,76,110,108,108,84,88,90,132,118,128,112,
%U A219028 138,162,150,114,156,120,142,176,150,128,132,136,198,188,184,190
%N A219028 Number of non-primitive roots for prime(n), less than prime(n).
%H A219028 Harvey P. Dale, <a href="/A219028/b219028.txt">Table of n, a(n) for n = 1..1000</a>
%F A219028 a(n) = p - 1 - phi(phi(p)), where p is the n-th prime.
%F A219028 a(n) = p - 1 - A008330(n) = p - 1 - A010554(p), where p is the n-th prime. - _V. Raman_, Nov 22 2012
%t A219028 Table[c=Prime[n];c-1-EulerPhi[EulerPhi[c]],{n,70}] (* _Harvey P. Dale_, Feb 12 2013 *)
%o A219028 (PARI) forprime(i=2,600,p=0;for(q=1,i-1,if(znorder(Mod(q,i))!=eulerphi(i),p++));print1(p","))
%Y A219028 Cf. A008330 (number of primitive roots for the n-th prime, less than n-th prime).
%Y A219028 Cf. A046144 (number of primitive roots for n, less than n).
%Y A219028 Cf. A010554 (value of phi(phi(n))).
%K A219028 nonn
%O A219028 1,3
%A A219028 _V. Raman_, Nov 10 2012