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A306097 Terms of A121707 not in A267999. 5


%S 697,1241,1247,1271,1513,2057,2201,2329,2501,2873,3053,3131,3683,3689,

%T 3961,4015,4061,4141,4777,4859,4991,5321,5921,5963,6137,6851,6953,

%U 7421,7769,7781,7957,8471,8711,8857,9017,9211,9271,9401,9641,9673,10217,10277,10489,10795,11033,11501

%N Terms of A121707 not in A267999.

%C Numbers n such that gcd(n, 2^n-2) > 1 and gcd(n, b^n-b) = 1 for some b > 2, b < n.

%C 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 2057 is the first term not in A008367, nor in A287391. - _M. F. Hasler_, Oct 04 2018

%H M. F. Hasler, <a href="/A306097/b306097.txt">Table of n, a(n) for n = 1..10000</a>

%F A121707 \ A267999.

%e The smallest element of this sequence is a(1) = 697 = 17*41.

%o (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 Cf. A121707, A267999.

%K nonn

%O 1,1

%A _M. F. Hasler_, following remarks from _Tomasz Ordowski_, Oct 03 2018

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Last modified June 1 02:09 EDT 2020. Contains 334758 sequences. (Running on oeis4.)