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 A127105 #22 Jul 21 2025 16:03:12 %S A127105 1,2,4,6,12,42,52,84,156,186,372,1092,1218,1302,1806,2436,2604,2756, %T A127105 3612,4836,5334,7212,8268,10668,12324,15918,18858,24492,31668,31836, %U A127105 33852,37716,37758,46956,50484,52374,55986,57876,71862,75516,86268 %N A127105 Numbers k such that k^2 divides 5^k-1. %C A127105 Subset of A067946 (numbers k such that k divides 5^k-1). %H A127105 Robert Israel, <a href="/A127105/b127105.txt">Table of n, a(n) for n = 1..1000</a> %H A127105 Taro Morishima, <a href="http://dx.doi.org/10.3792/pia/1195581610">Über die Fermatsche Vermutung</a>, Proc. Imp. Acad., Volume 4, Number 10 (1928), 590-592. %p A127105 select(t -> (5 &^t - 1) mod (t^2) = 0, [$1..10^5]); # _Robert Israel_, Jul 15 2018 %t A127105 Select[Range[30000], IntegerQ[(PowerMod[5, #, #^2 ]-1)/#^2 ]&] %o A127105 (PARI) isok(n) = Mod(5, n^2)^n == 1; \\ _Michel Marcus_, Apr 23 2017 %Y A127105 Cf. A127100, A127101, A127102, A127103, A123104, A127106, A127107, A127092. %Y A127105 Cf. A067946 (numbers k such that k divides 5^k-1). %K A127105 nonn %O A127105 1,2 %A A127105 _Alexander Adamchuk_, Jan 05 2007 %E A127105 More terms from _Ryan Propper_ and _Alexander Adamchuk_, Jan 05 2007