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 A319217 Integers k such that (13*2^k)^8 + 1 is prime. 1
 4, 9, 13, 38, 42, 67, 133, 134, 142, 155, 167, 226, 654, 5787, 6703, 12704, 25969, 70198, 78060, 235304 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS These numbers are a subset of Generalized Fermat Primes power 8. All numbers from 1 to 235763 has been checked by LLR, no other primes found. k is not congruent to 6 mod 25 because otherwise (13*2^k)^8+1 would be divisible by 401. - Bruno Berselli, Sep 21 2018 LINKS Table of n, a(n) for n=1..20. Chris K. Caldwell, The Prime Database: 815730721*2^1882432+1 EXAMPLE 4 is a term because (13*2^4)^8+1 = 3503536769037500417 is a prime number. MATHEMATICA Select[Range[700], PrimeQ[(13 2^#)^8 + 1] &] (* Vincenzo Librandi, Sep 21 2018 *) PROG (Magma) [n: n in [1..700] | IsPrime((13*2^n)^8+1)]; // Vincenzo Librandi, Sep 21 2018 (PARI) isok(k) = ispseudoprime((13*2^k)^8+1); \\ Altug Alkan, Sep 21 2018 CROSSREFS Sequence in context: A063606 A033287 A041323 * A041028 A041211 A042323 Adjacent sequences: A319214 A319215 A319216 * A319218 A319219 A319220 KEYWORD nonn,hard,more AUTHOR Lei Zhou, Sep 13 2018 STATUS approved

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Last modified June 4 03:55 EDT 2023. Contains 363118 sequences. (Running on oeis4.)