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 A086686 #6 Mar 17 2014 12:21:00
%S A086686 0,1,2,3,1,5,2,4,3,5,2,8,1,7,5,7,3,10,4,9,6,10,3,13,6,8,7,11,5,19,6,9,
%T A086686 7,9,6,18,5,13,9,16,5,22,7,16,13,12,9,19,7,16,11,15,8,21,12,16,14,14,
%U A086686 6,33,8,18,14,15,10,27,10,21,13,29,10,29,3,18,19
%N A086686 Number of 1<=i<n such that i*n-1 is prime.
%e A086686 For n=2, i=2 gives a prime (3), so a(2)=1.
%e A086686 For n=10, i=2,3,6,8,9 give primes, so a(10)=5.
%o A086686 (PARI) nphi(n)=local(c); c=0; for (i=1,n-1,if (isprime(i*n-1),c++)); c for(i=1,60,print1(","nphi(i)))
%o A086686 (PARI) a(n) = sum(i=1, n, isprime(i*n-1)); \\ _Michel Marcus_, Mar 17 2014
%K A086686 nonn
%O A086686 1,3
%A A086686 _Jon Perry_, Jul 28 2003
%E A086686 a(2) corrected and more terms from _Michel Marcus_, Mar 17 2014