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 A337829 #24 Oct 13 2020 15:43:20 %S A337829 3,7,43,53,127,163,487,677,883,2647,8527,8803,14407,18523,26407,32887, %T A337829 35323,39367,71443,105967,184087,184843,230203,265483,319327,388963, %U A337829 425083,543607,554527,651043,688087,690607,698923,796447,887923,924043,1001323 %N A337829 Odd integers k such that 5^((k-1)/2) + 1 == 0 (mod k*(k-1)/2). %C A337829 The first 564 terms are prime. %H A337829 Chai Wah Wu, <a href="/A337829/b337829.txt">Table of n, a(n) for n = 1..564</a> %t A337829 Select[Range[3, 10^6, 2], PowerMod[5, (# - 1)/2, (t = #*(# - 1)/2)] == t - 1 &] (* _Amiram Eldar_, Sep 24 2020 *) %Y A337829 Cf. A337818. %K A337829 nonn %O A337829 1,1 %A A337829 _Benoit Cloitre_, Sep 24 2020