A268657 - OEIS

%I #24 Apr 03 2023 10:36:13

%S 6,12,18,30,36,41,66,189,201,209,276,408,438,534,2208,3168,3189,3912,

%T 34350,42294,44685,48150,54792,55182,59973,80190,157169,213321,303093,

%U 382449,709968,801978,916773,1832496,2145353,2291610,2478785,5082306,7033641,10829346

%N 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 Wilfrid Keller, private communication, 2008.

%H Jeppe Stig Nielsen, <a href="/A268657/b268657.txt">Table of n, a(n) for n = 1..41</a>

%H 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 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 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 C. K. Caldwell, Top Twenty page, <a href="https://t5k.org/top20/page.php?id=28">Generalized Fermat Divisors (base=3)</a>

%H OEIS Wiki, <a href="/wiki/Generalized_Fermat_numbers">Generalized Fermat numbers</a>

%o (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 Cf. A059919, A268658, A204620, A268659, A268660, A268661, A268662, A268663, A226366, A268664. Subsequence of A002253.

%K nonn

%O 1,1

%A _Arkadiusz Wesolowski_, Feb 10 2016