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 A128679 #11 Jun 08 2021 02:22:53 %S A128679 1,3,21,609,903,2667,9429,15501,18543,26187,77343,108507,114681, %T A128679 159663,212541,273441,318507,405447,537747,797349,1197483,1357503, %U A128679 1398747,1731387,2354961,3146703,3325749,4451181,4630227,4665801,5192943 %N A128679 Numbers k such that k^3 divides 5^(k^2) + 1. %C A128679 3 divides a(n) for n > 1. 7 divides a(n) for n > 2. %t A128679 Select[Range[5*10^6], Mod[ 5^(#^2)+1, #^3]==0 &] (* _G. C. Greubel_, Jan 18 2018 *) %Y A128679 Cf. A127263 (numbers k such that k^3 divide 2^(k^2)+1). %Y A128679 Cf. A128677 (least k > p such that (k*p)^3 divides (p-1)^(k*p)^2+1, where p = prime(n) > 2). %Y A128679 Cf. A128678, A128680, A128681, A128682, A128683, A128684, A128685. %K A128679 hard,nonn %O A128679 1,2 %A A128679 _Alexander Adamchuk_, Mar 31 2007 %E A128679 More terms from _Ryan Propper_, Dec 31 2007