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 A014949 #21 Jun 28 2021 04:06:01
%S A014949 1,7,49,343,889,2359,2401,6223,16513,16807,43561,112903,115591,117649,
%T A014949 299593,304927,790321,794983,809137,823543,2033143,2097151,2134489,
%U A014949 5532247,5564881,5663959,5764801,13549249,14232001,14338681,14680057,14941423,34591207,38048311,38725729
%N A014949 Numbers k that divide 8^k - 1.
%C A014949 For all m, 7^m is in the sequence. - _Benoit Cloitre_, Mar 05 2002
%C A014949 From _Alexander Adamchuk_, May 16 2010: (Start)
%C A014949 7 divides a(n) for n>1.
%C A014949 Prime divisors of a(n) in the order of their first appearance are {7, 127, 337, 2287, 15241, 14407, 18199, 42463, ...}. (End)
%H A014949 M. F. Hasler, <a href="/A014949/b014949.txt">Table of n, a(n) for n = 1..64</a>
%o A014949 (PARI) is(n)=Mod(8,n)^n==1 \\ _Charles R Greathouse IV_, Nov 04 2016
%Y A014949 Cf. A024088 (8^n-1).
%K A014949 nonn
%O A014949 1,2
%A A014949 _Olivier Gérard_
%E A014949 More terms from _Benoit Cloitre_, Mar 05 2002
%E A014949 a(15)-a(31) from _Alexander Adamchuk_, May 16 2010
%E A014949 More terms from _M. F. Hasler_, Nov 21 2018