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A081507 Numbers k for which 2^k + 3^k + 4^k is prime. 2
0, 2, 4, 6, 8, 108, 144, 334, 1422, 4824, 16502, 19050, 23262 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
a(13) > 20838. - J.W.L. (Jan) Eerland, Dec 20 2021
LINKS
EXAMPLE
k=2: 2^2 + 3^2 + 4^2 = 4 + 9 + 16 = 29 (a prime).
MATHEMATICA
Do[s=2^w+3^w+4^w; If[IntegerQ[w/100], Print[{w}]]; If[PrimeQ[s], Print[{w, s}]], {w, 0, 1000}]
Do[ If[ PrimeQ[2^w+3^w+4^w], Print[n]], {n, 0, 5000}]
Select[Range[5000], PrimeQ[Plus@@({2, 3, 4}^#)]&] (* Harvey P. Dale, Jan 03 2011 *)
DeleteCases[ParallelTable[If[PrimeQ[(2^n)+(3^n)+(4^n)], n, a], {n, 0, 19050}], a] (* J.W.L. (Jan) Eerland, Dec 20 2021 *)
PROG
(PARI) isok(k) = isprime(2^k + 3^k + 4^k); \\ Michel Marcus, Sep 05 2017
(Magma) [n: n in [0..400] | IsPrime(2^n+3^n+4^n)]; // Vincenzo Librandi, Sep 05 2017
CROSSREFS
Cf. A081506.
Sequence in context: A083145 A085920 A228327 * A115336 A119666 A087302
KEYWORD
nonn,more
AUTHOR
Labos Elemer, Apr 15 2003
EXTENSIONS
a(9)-a(10) from Robert G. Wilson v, Jul 22 2005
a(11)-a(12) from J.W.L. (Jan) Eerland, Dec 20 2021
Offset corrected by Jon E. Schoenfield, Dec 20 2021
a(13) from Michael S. Branicky, Mar 31 2023
STATUS
approved

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Last modified April 18 11:52 EDT 2024. Contains 371779 sequences. (Running on oeis4.)