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URL: https://oeis.org/A002958

⇱ A002958 - OEIS

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A002958
Numbers k such that 2*25^k - 1 is prime.
4
2, 3, 8, 12, 15, 27, 48, 89, 137, 666, 1383, 1530, 2102, 8868, 95031, 111768, 130200, 341540
OFFSET
1,1
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
C. R. Zarnke and H. C. Williams, Computer determination of some large primes, pp. 563-570 in Proceedings of the Louisiana Conference on Combinatorics, Graph Theory and Computer Science. Vol. 2, edited R. C. Mullin et al., 1971.
MATHEMATICA
Do[m = n; If[PrimeQ[2*25^n - 1], Print[n]], {n, 1, 10^3}]
Select[Range[0, 5000], PrimeQ[(2*25^# - 1)] &] (* Vincenzo Librandi, Sep 25 2012 *)
PROG
(PARI) is(n)=ispseudoprime(2*25^n-1) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
Sequence in context: A192113 A243192 A164817 * A290153 A266629 A249096
KEYWORD
nonn,hard,more
EXTENSIONS
a(10) from Robert G. Wilson v, Nov 02 2000
a(11)-a(13) from Vincenzo Librandi, Sep 25 2012
a(14)-a(17) (from A120375) from Joerg Arndt, Jun 15 2020
a(18) (from A120375) by Jorge Coveiro, Jun 20 2020
STATUS
approved