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 A068000 #11 Apr 22 2025 02:44:08
%S A068000 1,2,5,18,63
%N A068000 Numbers k such that (k! + 1) == 0 ( mod prime(k) ).
%C A068000 There are no other terms below 33333. Is 63 the last term? - Hauke Worpel (hw1(AT)email.com), May 24 2003
%C A068000 There are no other terms below 534000. - _Rick L. Shepherd_, May 26 2003
%C A068000 There are no other terms below 10^7. - _Amiram Eldar_, Apr 22 2025
%t A068000 Do[ If[ Mod[n! + 1, Prime[n]] == 0, Print[n]], {n, 1, 10000} ]
%o A068000 (PARI) for(k=1, 33333, if( (k!+1)%prime(k)==0, print1(k, ", ")))
%o A068000 (PARI) list(lim) = {my(k = 0, r = 1); forprime(p = 1, lim, k++; r *= k; if(!((r+1) % p), print1(k, ", ")));} \\ _Amiram Eldar_, Apr 22 2025
%Y A068000 Cf. A067999, A066953.
%K A068000 nonn,hard,more
%O A068000 1,2
%A A068000 _Robert G. Wilson v_, Feb 08 2002