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 A127102 #15 Jul 21 2025 16:01:33 %S A127102 1,7,889,2359,299593,2033143,13549249,42931441,100170217,310935751, %T A127102 685169191,3606045247,4566096913,5452293007,6620620783,12721617559, %U A127102 30987132463,65576560063,92349997537,104785348087,457967746369 %N A127102 Numbers k such that k^2 divides 8^k-1. %C A127102 Subsequence of A014949. %C A127102 a(5) = 299593 = (8^7-1)/7 is a repunit in base 8, 1111111(base 8). The first 5 listed terms of a(n) are terms of the finite sequence A003530: divisors of 8^7-1. [Corrected and edited by _M. F. Hasler_, Nov 21 2018] %C A127102 Also a subsequence of A177908, see there for more comments on properties of terms of this sequence. - _M. F. Hasler_, Nov 21 2018 %t A127102 Select[Range[20000], IntegerQ[(PowerMod[8, #, #^2 ]-1)/#^2 ]&] %o A127102 (PARI) is(n)=Mod(8,n^2)^n==1 \\ _M. F. Hasler_, Nov 21 2018 %Y A127102 Cf. A127100, A127101, A127103, A127104, A127105, A127106, A127107, A127092, A014949, A003530. %K A127102 nonn %O A127102 1,2 %A A127102 _Alexander Adamchuk_, Jan 05 2007, Jan 07 2007 %E A127102 More terms from _Ryan Propper_, Jan 05 2007 %E A127102 Terms a(12) onward from _Max Alekseyev_, May 06 2010