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A059569
Numbers k such that (7*3^k - 5)/2 is prime.
1
2, 4, 6, 8, 38, 66, 72, 126, 140, 152, 174, 332, 710, 820, 2528, 2582, 2668, 2776, 2982, 3826, 6144, 15778, 23518, 75504
OFFSET
1,1
COMMENTS
a(23) > 20306. - Jinyuan Wang, Jan 29 2020
MATHEMATICA
Do[ If[ PrimeQ[ (7*3^n - 5)/2 ], Print[n] ], {n, 0, 4500} ]
PROG
(PARI) is(n)=ispseudoprime((7*3^n-5)/2) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
Cf. A059528 ((7*3^k+5)/2 is prime).
Sequence in context: A329887 A108425 A215216 * A083433 A083435 A163502
KEYWORD
nonn,more
AUTHOR
Robert G. Wilson v, Feb 16 2001
EXTENSIONS
a(21)-a(22) from Jinyuan Wang, Jan 29 2020
a(23) from Michael S. Branicky, May 02 2023
a(24) from Michael S. Branicky, Oct 24 2024
STATUS
approved