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A059622 Numbers k such that (5*3^k - 7)/2 is prime. 1
2, 4, 16, 24, 32, 40, 120, 124, 144, 172, 186, 376, 700, 1232, 1264, 2894, 5054, 14826, 16498, 18348, 33416 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
a(21) > 20000. - Jinyuan Wang, Jan 28 2020
LINKS
MATHEMATICA
Do[ If[ PrimeQ[ (5*3^n - 7)/2 ], Print[n] ], {n, 0, 10000} ]
Select[Range[5100], PrimeQ[(5*3^#-7)/2]&] (* Harvey P. Dale, Jul 15 2018 *)
PROG
(PARI) is(n)=ispseudoprime((5*3^n-7)/2) \\ Charles R Greathouse IV, Jun 13 2017
(Magma) [k: k in [0..1000] | IsPrime((5*3^k - 7) div 2)]; // Jinyuan Wang, Jan 28 2020
CROSSREFS
Cf. A059621 ((5*3^k+7)/2 is prime).
Sequence in context: A193868 A256788 A324211 * A131475 A239363 A045541
KEYWORD
nonn,more
AUTHOR
Robert G. Wilson v, Feb 19 2001
EXTENSIONS
a(18)-a(20) from Jinyuan Wang, Jan 28 2020
a(21) from Michael S. Branicky, Apr 29 2023
STATUS
approved

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Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)