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A268657 Numbers k such that 3*2^k + 1 is a prime factor of a generalized Fermat number 3^(2^m) + 1 for some m.

%I A268657 #24 Apr 03 2023 10:36:13
%S A268657 6,12,18,30,36,41,66,189,201,209,276,408,438,534,2208,3168,3189,3912,
%T A268657 34350,42294,44685,48150,54792,55182,59973,80190,157169,213321,303093,
%U A268657 382449,709968,801978,916773,1832496,2145353,2291610,2478785,5082306,7033641,10829346
%N A268657 Numbers k such that 3*2^k + 1 is a prime factor of a generalized Fermat number 3^(2^m) + 1 for some m.
%D A268657 Wilfrid Keller, private communication, 2008.
%H A268657 Jeppe Stig Nielsen, <a href="/A268657/b268657.txt">Table of n, a(n) for n = 1..41</a>
%H A268657 Anders Björn and Hans Riesel, <a href="http://dx.doi.org/10.1090/S0025-5718-98-00891-6">Factors of generalized Fermat numbers</a>, Math. Comp. 67 (1998), no. 221, pp. 441-446.
%H A268657 Anders Björn and Hans Riesel, <a href="http://dx.doi.org/10.1090/S0025-5718-05-01816-8">Table errata to “Factors of generalized Fermat numbers”</a>, Math. Comp. 74 (2005), no. 252, p. 2099.
%H A268657 Anders Björn and Hans Riesel, <a href="http://dx.doi.org/10.1090/S0025-5718-10-02371-9">Table errata 2 to "Factors of generalized Fermat numbers"</a>, Math. Comp. 80 (2011), pp. 1865-1866.
%H A268657 C. K. Caldwell, Top Twenty page, <a href="https://t5k.org/top20/page.php?id=28">Generalized Fermat Divisors (base=3)</a>
%H A268657 OEIS Wiki, <a href="/wiki/Generalized_Fermat_numbers">Generalized Fermat numbers</a>
%o A268657 (PARI) for(k=1,+oo,p=3*2^k+1;if(ispseudoprime(p),t=znorder(Mod(3,p));bitand(t,t-1)==0&&print1(k,", "))) \\ _Jeppe Stig Nielsen_, Oct 30 2020
%Y A268657 Cf. A059919, A268658, A204620, A268659, A268660, A268661, A268662, A268663, A226366, A268664. Subsequence of A002253.
%K A268657 nonn
%O A268657 1,1
%A A268657 _Arkadiusz Wesolowski_, Feb 10 2016