cp's OEIS Frontend

A273946 Odd prime factors of generalized Fermat numbers of the form 5^(2^m) + 1 with m >= 0.

%I A273946 #14 Apr 03 2023 10:36:13
%S A273946 3,13,17,257,313,641,769,2593,11489,19457,65537,163841,786433,1503233,
%T A273946 1655809,7340033,14155777,18395137,23606273,29423041,39714817,
%U A273946 75068993,167772161,2483027969,4643094529,6616514561,47148957697,241931001601,2748779069441
%N A273946 Odd prime factors of generalized Fermat numbers of the form 5^(2^m) + 1 with m >= 0.
%C A273946 Odd primes p such that the multiplicative order of 5 (mod p) is a power of 2.
%D A273946 Hans Riesel, Common prime factors of the numbers A_n=a^(2^n)+1, BIT 9 (1969), pp. 264-269.
%H A273946 Arkadiusz Wesolowski, <a href="/A273946/b273946.txt">Table of n, a(n) for n = 1..37</a>
%H A273946 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 A273946 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 A273946 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 A273946 C. K. Caldwell, Top Twenty page, <a href="https://t5k.org/top20/page.php?id=29">Generalized Fermat Divisors (base=5)</a>
%H A273946 Harvey Dubner and Wilfrid Keller, <a href="http://dx.doi.org/10.1090/S0025-5718-1995-1270618-1">Factors of Generalized Fermat Numbers</a>, Math. Comp. 64 (1995), no. 209, pp. 397-405.
%H A273946 OEIS Wiki, <a href="/wiki/Generalized_Fermat_numbers">Generalized Fermat numbers</a>
%t A273946 Select[Prime@Range[2, 10^5], IntegerQ@Log[2, MultiplicativeOrder[5, #]] &]
%Y A273946 Cf. A023394, A072982, A199591, A268658, A268662, A273945 (base 3), A273947 (base 6), A273948 (base 7), A273949 (base 11), A273950 (base 12).
%K A273946 nonn
%O A273946 1,1
%A A273946 _Arkadiusz Wesolowski_, Jun 05 2016