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 A057245 #44 Jun 09 2025 20:25:49 %S A057245 1,3,9,11,33,99 %N A057245 Numbers m such that m | Sum_{k=1..m} k!. %C A057245 n such that A067462(n) = 0. - _T. D. Noe_, May 13 2010 %C A057245 For any terms in this sequence, their LCM also belongs to this sequence. Term a(7), if it exists, is prime. - _Max Alekseyev_, Oct 14 2012 %C A057245 n > 1 is in this sequence iff A049782(n) = 1. - _Max Alekseyev_, Apr 17 2016 %C A057245 If it exists, a(7) > 12000000. - _Bert Dobbelaere_, Oct 28 2018 %C A057245 If it exists, a(7) > 1.6*10^8. - _Giovanni Resta_, Nov 09 2018 %D A057245 Richard K. Guy, Unsolved Problems in Number Theory, Springer, Third Ed., 2004, Section B44. %t A057245 a = 0; b = 1; k = 2; While[k < 250001, c = k*b - (k - 1) a; %t A057245 If[ Mod[c, k] == 1, Print[k]]; a = b; b = c; k++] (* _Robert G. Wilson v_, Jun 15 2013 *) %o A057245 (GAP) Filtered([1..1500],m->Sum([1..m],k->Factorial(k)) mod m = 0); # _Muniru A Asiru_, Oct 28 2018 %Y A057245 Cf. A007489, A049782, A064383. %K A057245 nonn,hard,more %O A057245 1,2 %A A057245 _Robert G. Wilson v_, Sep 21 2000