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 A242865 #46 Feb 07 2020 13:35:04 %S A242865 3,9299,31903,50963,87043,115918,116891,219827,241043,394243,550243, %T A242865 617503,760243,806623,1029253,1050787,1458083,1642798,1899458,2864755, %U A242865 3205387,3588115,3839363,4164578,5041223,5610583,5834755,5977555,7837903,8005558,8067433,8128823,9007603,9298903,9449113,9617443,9835843 %N A242865 Numbers n such that 3^(n - 3) is congruent to 1 modulo n. %H A242865 Daniel Starodubtsev, <a href="/A242865/b242865.txt">Table of n, a(n) for n = 1..372</a> (terms 1..163 from Felix Fröhlich) %t A242865 Select[Range[10^4], Mod[3^(# - 3), #] == 1 &] (* _Alonso del Arte_, May 27 2014 *) %o A242865 (PARI) for(n=3, 10^6, if(Mod(3, n)^(n-3)==1, print1(n, ", "))) %Y A242865 Cf. A067945, A173572. %Y A242865 Intersection with A033553 gives A277344. %K A242865 nonn %O A242865 1,1 %A A242865 _Felix Fröhlich_, May 24 2014