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A283653
Numbers k such that 3^k + (-2)^k is prime.
4
0, 2, 3, 4, 5, 17, 29, 31, 53, 59, 101, 277, 647, 1061, 2381, 2833, 3613, 3853, 3929, 5297, 7417, 90217, 122219, 173191, 256199, 336353, 485977, 591827, 1059503
OFFSET
1,2
COMMENTS
Numbers j such that both 3^j + (-2)^j and 3^j + (-4)^j are primes: 0, 3, 4, 17, 59, ...
See Michael Somos comment in A082101.
Probably this is just A057468 with 0,2,4 added, because we already know that if another even number belong to this sequence it must be greater than log_3(10^16000000) = about 3.3*10^7. This is because 3^n+2^n can be a prime with n>0 only if n is a power of 2. - Giovanni Resta, Mar 12 2017
EXAMPLE
4 is in this sequence because 3^4 + (-2)^4 = 97 is prime.
MATHEMATICA
Select[Range[0, 10000], PrimeQ[3^# + (-2)^#] &] (* G. C. Greubel, Jul 29 2018 *)
PROG
(Magma) [n: n in [0..1000] | IsPrime(3^n+(-2)^n)];
(PARI) is(n)=isprime(3^n+(-2)^n) \\ Charles R Greathouse IV, Mar 16 2017
CROSSREFS
Cf. A174326. Subsequence of A087451. Supersequence of A057468.
Cf. A082101.
Sequence in context: A117885 A030574 A325652 * A375638 A162657 A333046
KEYWORD
nonn,more
AUTHOR
STATUS
approved