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 A242754 #14 May 23 2014 00:43:41
%S A242754 2,3,4,6,7,10,11,13,17,18,21,31,37,40,41,46,48,49,52,53,58,60,64,66,
%T A242754 70,71,72,73,75,81,85,92,93,96,100,102,109,117,119,127,136,137,140,
%U A242754 143,145,146,149,160,162,179,189,194,200,206,215,232,233,243,246,247
%N A242754 Positive integers k such that k*p == 1 (mod prime(k)) for some prime p < prime(k).
%C A242754 According to the conjecture in A242753, this sequence should have infinitely many terms.
%C A242754 Conjecture: The number of terms not exceeding x > 1 has the main term x/(log x) as x tends to infinity.
%H A242754 Zhi-Wei Sun, <a href="/A242754/b242754.txt">Table of n, a(n) for n = 1..10000</a>
%e A242754 a(4) = 6 since 6*11 == 1 (mod prime(6)=13) with 11 prime, but 5*9 == 1 (mod prime(5)=11) with 9 composite.
%t A242754 p[n_]:=PrimeQ[PowerMod[n,-1,Prime[n]]]
%t A242754 n=0;Do[If[p[k],n=n+1;Print[n," ",k]];Continue,{k,1,247}]
%Y A242754 Cf. A000040, A000720, A242425, A242748, A242750, A242752, A242753, A242755.
%K A242754 nonn
%O A242754 1,1
%A A242754 _Zhi-Wei Sun_, May 22 2014