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A219045
Numbers k such that 3^k - 26 is prime.
16
7, 10, 13, 22, 27, 30, 57, 62, 117, 255, 535, 651, 873, 998, 1502, 18145, 22766, 25770, 43558, 45663, 48058, 62887, 87477, 103585, 115802
OFFSET
1,1
COMMENTS
a(26) > 2*10^5. - Robert Price, Nov 20 2013
EXAMPLE
3^7 - 26 = 2161 (prime), so 7 is in the sequence.
MATHEMATICA
Do[If[PrimeQ[3^n - 26], Print[n]], {n, 3, 10000}]
PROG
(PARI) is(n)=isprime(3^n-26) \\ Charles R Greathouse IV, Feb 17 2017
CROSSREFS
Cf. Sequences of numbers k such that 3^k + m is prime:
(m = 2) A051783, (m = -2) A014224, (m = 4) A058958, (m = -4) A058959,
(m = 8) A217136, (m = -8) A217135, (m = 10) A217137, (m = -10) A217347,
(m = 14) A219035, (m = -14) A219038, (m = 16) A205647, (m = -16) A219039,
(m = 20) A219040, (m = -20) A219041, (m = 22) A219042, (m = -22) A219043,
(m = 26) A219044, (m = -26) A219045, (m = 28) A219046, (m = -28) A219047,
(m = 32) A219048, (m = -32) A219049, (m = 34) A219050, (m = -34) A219051. Note that if m is a multiple of 3, 3^k + m is also a multiple of 3 (for k greater than 0), and as such isn't prime.
Sequence in context: A007770 A212979 A114961 * A199427 A178508 A123834
KEYWORD
nonn,more
AUTHOR
Nicolas M. Perrault, Nov 10 2012
EXTENSIONS
a(16)-a(25) from Robert Price, Nov 20 2013
STATUS
approved