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 A242755 #8 May 23 2014 00:43:55
%S A242755 3,5,7,13,17,29,31,41,59,61,73,127,157,173,179,199,223,227,239,241,
%T A242755 271,281,311,317,349,353,359,367,379,419,439,479,487,503,541,557,599,
%U A242755 643,653,709,769,773,809,823,829,839,859,941,953,1063
%N A242755 Primes p such that pi(p)*q == 1 (mod p) for some prime q < p, where pi(p) is the number of primes not exceeding p.
%C A242755 According to the conjecture in A242753, this sequence should contain infinitely many primes.
%C A242755 Conjecture: The number of such primes not exceeding x > 1 has the main term x/(log x)^2 as x tends to infinity.
%H A242755 Zhi-Wei Sun, <a href="/A242755/b242755.txt">Table of n, a(n) for n = 1..10000</a>
%e A242755 a(4) = 13 since 13 is prime with pi(13) = 6, and 6*11 == 1 (mod 13) with 11 prime, but pi(11)*9 == 1 (mod 11) with 9 not prime.
%t A242755 p[n_]:=PrimeQ[PowerMod[n,-1,Prime[n]]]
%t A242755 n=0;Do[If[p[k],n=n+1;Print[n," ",Prime[k]]];Continue,{k,1,179}]
%Y A242755 Cf. A000040, A000720, A242748, A242750, A242752, A242753, A242754.
%K A242755 nonn
%O A242755 1,1
%A A242755 _Zhi-Wei Sun_, May 22 2014