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 A273949 Odd prime factors of generalized Fermat numbers of the form 11^(2^m) + 1 with m >= 0. 8
 3, 17, 61, 193, 257, 7321, 15361, 51329, 65537, 163841, 6304673, 15190529, 70254593, 1691123713, 1760464897, 3221225473, 3489660929, 4696846849, 6874464257, 53401878529, 111489577217, 149300051969, 184683593729, 206158430209, 447600088289, 1819992391681 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Odd primes p other than 5 such that the multiplicative order of 11 (mod p) is a power of 2. REFERENCES Hans Riesel, Common prime factors of the numbers A_n=a^(2^n)+1, BIT 9 (1969), pp. 264-269. LINKS Arkadiusz Wesolowski, Table of n, a(n) for n = 1..31 Anders Björn and Hans Riesel, Factors of generalized Fermat numbers, Math. Comp. 67 (1998), no. 221, pp. 441-446. Anders Björn and Hans Riesel, Table errata to “Factors of generalized Fermat numbers”, Math. Comp. 74 (2005), no. 252, p. 2099. Anders Björn and Hans Riesel, Table errata 2 to "Factors of generalized Fermat numbers", Math. Comp. 80 (2011), pp. 1865-1866. Harvey Dubner and Wilfrid Keller, Factors of Generalized Fermat Numbers, Math. Comp. 64 (1995), no. 209, pp. 397-405. OEIS Wiki, Generalized Fermat numbers MATHEMATICA Delete[Select[Prime@Range[2, 10^5], IntegerQ@Log[2, MultiplicativeOrder[11, #]] &], 2] CROSSREFS Cf. A023394, A072982, A199592, A273945 (base 3), A273946 (base 5), A273947 (base 6), A273948 (base 7), A273950 (base 12). Sequence in context: A226719 A168547 A208996 * A174285 A227427 A120386 Adjacent sequences:  A273946 A273947 A273948 * A273950 A273951 A273952 KEYWORD nonn AUTHOR Arkadiusz Wesolowski, Jun 05 2016 STATUS approved

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Last modified August 4 15:50 EDT 2020. Contains 336202 sequences. (Running on oeis4.)