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 A058934 Numbers n such that 2*5^n + 1 is prime. 1
 0, 1, 3, 13, 45, 105, 159, 297, 1443, 2977, 3699, 11709, 12357, 43165, 121995 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS a(n) is odd for n>0. Next term > 17200. - Julián Aguirre, Apr 22 2011 a(16) > 2*10^5. - Robert Price, Mar 14 2015 LINKS EXAMPLE a(3)=13 and 1+2*5^13=2441406251 is prime. MATHEMATICA Select[Range[0, 16000], PrimeQ[2*5^#+1]&] (* Julián Aguirre, Apr 22 2011 *) PROG (Sage) for n in range(16000): ...if is_prime(2*5^n+1): ...print(n) ## Julián Aguirre, Apr 22 2011 (PARI) is(n)=ispseudoprime(2*5^n+1) \\ Charles R Greathouse IV, Jun 12 2017 CROSSREFS Cf. A003306 (2*3^n + 1 is prime), A120375 (2*5^n-1 is prime). Sequence in context: A095863 A136520 A212416 * A141088 A187915 A115128 Adjacent sequences:  A058931 A058932 A058933 * A058935 A058936 A058937 KEYWORD nonn AUTHOR Labos Elemer, Jan 12 2001 EXTENSIONS Edited by Joerg Arndt, Apr 22 2011 Terms 1443,...,12357 from Julián Aguirre, Apr 22 2011 a(14)-a(15) from Robert Price, Mar 14 2015 STATUS approved

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Last modified April 18 13:05 EDT 2019. Contains 322209 sequences. (Running on oeis4.)