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 A259505 #20 Dec 25 2015 03:03:32
%S A259505 997,8647,47521,85991,283411,4594451,5476381,52728733,53920829,
%T A259505 100980223,127072849,436118521,585293099,858905011
%N A259505 Primes p where an integer r with 1 < r < p exists such that r^r == 1 (mod p^2).
%C A259505 Inspired by the Nov 28 2014 comment from Thomas Ordowski in A001220.
%C A259505 a(5) > 276929 if it exists.
%C A259505 a(15) > 10^9. - _Hiroaki Yamanouchi_, Dec 19 2015
%e A259505 252^252 = 1 mod 997^2.
%e A259505 5764^5764 = 1 mod 8647^2.
%t A259505 p = 2; lst = {}; While[p < 100001, r = 2; While[r < p, If[ PowerMod[r, r, p^2] == 1, AppendTo[lst, p]]; r++]; p = NextPrime@ p] (* _Robert G. Wilson v_, Dec 06 2015 *)
%o A259505 (PARI) forprime(p=1, , for(r=2, p-1, if(Mod(r, p^2)^r==1, print1(p, ", "); break({1}))))
%Y A259505 Cf. A001220, A134307.
%K A259505 nonn,hard,more
%O A259505 1,1
%A A259505 _Felix Fröhlich_, Nov 08 2015
%E A259505 a(5)-a(14) from _Hiroaki Yamanouchi_, Dec 19 2015