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 A128680 #12 Jun 08 2021 02:22:49 %S A128680 1,7,203,1379,11977,39991,577129,2359469,4780447,6521291,6640739, %T A128680 9904979,21511301,28434413,34050611,113694413,189117439,222281549, %U A128680 250163599,282046373,391803601,941748059,1269166759,1308225583 %N A128680 Numbers k such that k^3 divides 6^(k^2) + 1. %C A128680 7 divides a(n) for n > 1. %t A128680 Select[Range[5*10^6], Mod[ 6^(#^2)+1, #^3]==0 &] (* _G. C. Greubel_, Jan 18 2018 *) %Y A128680 Cf. A127263 (numbers k such that k^3 divide 2^(k^2)+1). %Y A128680 Cf. A128677 (least k > p such that (k*p)^3 divides (p-1)^(k*p)^2+1, where p = prime(n) > 2). %Y A128680 Cf. A128678, A128679, A128681, A128682, A128683, A128684, A128685. %K A128680 hard,nonn %O A128680 1,2 %A A128680 _Alexander Adamchuk_, Mar 31 2007 %E A128680 More terms from _Ryan Propper_, Jan 13 2008