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 A337830 #30 Aug 04 2025 01:06:52 %S A337830 2843,2390123,9893003,16236347,46353707,334358459,564092747,584214107, %T A337830 1640200619,2010092603,14044030043,22315857803,23753097803, %U A337830 92758244699,136542051227,281195463179,332945964107,545960571227 %N A337830 Odd integers k such that 6^((k-1)/2) + 1 == 0 (mod k*(k-1)/2). %C A337830 Computed terms are prime. %C A337830 Conjecture: a(n) == 1 mod 406 for n > 5. - _Chai Wah Wu_, Oct 07 2020 %t A337830 Select[Range[3, 10^7, 2], PowerMod[6, (# - 1)/2, (t = #*(# - 1)/2)] == t - 1 &] (* _Amiram Eldar_, Sep 24 2020 *) %Y A337830 Cf. A337818. %K A337830 nonn,more %O A337830 1,1 %A A337830 _Benoit Cloitre_, Sep 24 2020 %E A337830 a(6)-a(13) from _Amiram Eldar_, Sep 24 2020 %E A337830 a(14)-a(15) from _Bill McEachen_, Jul 21 2025 %E A337830 a(16)-a(18) from _Bill McEachen_, Aug 03 2025