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A058958
Numbers k such that 3^k + 4 is prime.
27
0, 1, 2, 3, 6, 9, 10, 22, 30, 42, 57, 87, 174, 195, 198, 562, 994, 2421, 2487, 4629, 5838, 13698, 14730, 16966, 25851, 98634, 117222, 192819, 226038, 296115, 318465, 355902
OFFSET
1,3
COMMENTS
Next term > 15000. The primes corresponding to 4629, ..., 14730 pass PARI's ispseudoprime() and the Rabin-Miller test for the first 100 prime bases. - Joerg Arndt, Jul 19 2012
Used PFGW (Fermat and Lucas, BLS) to determine (probable) primality of a(24)-a(26). - Robert Price, Jun 30 2013
a(27) > 10^5. - Robert Price, Jun 30 2013
a(29) > 2*10^5. - Robert Price, Dec 10 2013
a(31) > 3*10^5. - Tyler NeSmith, Dec 10 2020
MATHEMATICA
Do[ If[ PrimeQ[3^n + 4], Print[n] ], {n, 0, 3000} ]
Select[Range[0, 3000], PrimeQ[3^#+4]&] (* Harvey P. Dale, Sep 07 2022 *)
PROG
(PARI) for(n=0, 10^5, if(ispseudoprime(3^n+4), print1(n, ", "))); /* Joerg Arndt, Jul 19 2012 */
(Magma) [n: n in [0..700] | IsPrime(3^n+4)]; // Vincenzo Librandi, Aug 25 2015
CROSSREFS
Cf. A102903 (corresponding primes).
Sequence in context: A191127 A015898 A157217 * A215618 A189708 A127590
KEYWORD
nonn,hard,more
AUTHOR
Robert G. Wilson v, Jan 13 2001
EXTENSIONS
Terms 4629 ... 14730 from Joerg Arndt, Jul 19 2012
0 added by Bruno Berselli, Oct 04 2012
a(24)-a(26) from Robert Price, Jun 30 2013
a(27)-a(28) from Robert Price, Dec 10 2013
a(29)-a(30) from Tyler NeSmith, Dec 10 2020
a(31)-a(32) from Aurelien Gibier, Oct 02 2024
STATUS
approved