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A217351
Numbers k such that 6^k + 7 is prime.
3
1, 2, 3, 4, 6, 21, 24, 27, 30, 54, 70, 126, 369, 435, 612, 787, 1275, 2155, 2436, 5734, 6016, 16107, 25786, 34266, 38841, 45834, 46584
OFFSET
1,2
MATHEMATICA
Select[Range[10000], PrimeQ[6^# + 7] &]
PROG
(PARI) is(n)=ispseudoprime(6^n+7) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
Cf. A104115 (associated primes).
Sequence in context: A220702 A342503 A369773 * A274238 A115035 A219048
KEYWORD
nonn,more,hard
AUTHOR
Vincenzo Librandi, Oct 02 2012
EXTENSIONS
a(20)-a(21) from Bruno Berselli, Oct 04 2012
a(22)-a(23) from Michael S. Branicky, Apr 30 2023
a(24)-a(27) from Michael S. Branicky, Sep 19 2024
STATUS
approved