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 A306097 #7 Oct 04 2018 10:47:23
%S A306097 697,1241,1247,1271,1513,2057,2201,2329,2501,2873,3053,3131,3683,3689,
%T A306097 3961,4015,4061,4141,4777,4859,4991,5321,5921,5963,6137,6851,6953,
%U A306097 7421,7769,7781,7957,8471,8711,8857,9017,9211,9271,9401,9641,9673,10217,10277,10489,10795,11033,11501
%N A306097 Terms of A121707 not in A267999.
%C A306097 Numbers n such that gcd(n, 2^n-2) > 1 and gcd(n, b^n-b) = 1 for some b > 2, b < n.
%C A306097 Or: Numbers n such that gcd(n, 2^n-2) > 1 and for every prime factor p of n, p-1 does not divide n-1.
%C A306097 2057 is the first term not in A008367, nor in A287391. - _M. F. Hasler_, Oct 04 2018
%H A306097 M. F. Hasler, <a href="/A306097/b306097.txt">Table of n, a(n) for n = 1..10000</a>
%F A306097 A121707 \ A267999.
%e A306097 The smallest element of this sequence is a(1) = 697 = 17*41.
%o A306097 (PARI) is(n,p)={for(i=1, #p=factor(n)[,1], (n-1)%(p[i]-1)||return); gcd(n, lift(Mod(2,n)^n-2))>1}
%Y A306097 Cf. A121707, A267999.
%K A306097 nonn
%O A306097 1,1
%A A306097 _M. F. Hasler_, following remarks from _Tomasz Ordowski_, Oct 03 2018