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A109387
Numbers k such that 3^k - k^3 is prime.
11
1, 4, 10, 52, 112, 212, 346, 406, 512, 13904, 76610, 89746, 114892
OFFSET
1,2
COMMENTS
Terms <= 512 correspond to certified primes. Next term after 13904 is greater than 20000.
EXAMPLE
4 is a term because 3^4 - 4^3 = 17 is prime.
3^10 - 10^3 = 58049 is prime, hence 10 is a term.
MATHEMATICA
Do[If[PrimeQ[3^n - n^3], Print[n]], {n, 1, 20000}]
PROG
(PARI) is(n)=isprime(3^n-n^3) \\ Charles R Greathouse IV, Feb 17 2017
CROSSREFS
Sequence in context: A351046 A208236 A032495 * A362819 A018844 A007027
KEYWORD
hard,more,nonn
AUTHOR
Ryan Propper, Jun 26 2005
EXTENSIONS
Two more terms from Donovan Johnson, Feb 26 2008
a(13) from Norbert Schneider submitted by Robert Price, Mar 16 2019
STATUS
approved