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 A253471 Numbers k such that 3^k + k^3 is prime. 2
 2, 56, 10112, 63880, 78296, 125330, 222748, 1839730 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All terms == 2 or 4 mod 6. - Robert Israel, Jan 01 2015 LINKS Table of n, a(n) for n=1..8. EXAMPLE 2 is in the sequence because 3^2 + 2^3 = 17 is prime. 56 is in the sequence because 3^56 + 56^3 = 523347633027360537213687137 is prime. MAPLE select(t -> isprime(3^t+t^3), [seq(seq(6*i+j, j=[2, 4]), i=0..100)]); # Robert Israel, Jan 01 2015 MATHEMATICA Do[If[PrimeQ[3^n+n^3], Print[n]], {n, 0, 12000}] PROG (PARI) is(n)=ispseudoprime(3^n+n^3) \\ Charles R Greathouse IV, Jun 06 2017 CROSSREFS Cf. A001585 (3^n + n^3), A064539 (2^n + n^2 is prime), A094133 (Leyland primes). Sequence in context: A206305 A325291 A326551 * A230879 A080318 A002542 Adjacent sequences: A253468 A253469 A253470 * A253472 A253473 A253474 KEYWORD nonn,hard,more AUTHOR Michel Lagneau, Jan 01 2015 EXTENSIONS a(4)-a(7) from Hans Havermann, Apr 30 2015 a(8) from Ryan Propper, Jun 27 2023 STATUS approved

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Last modified March 4 10:39 EST 2024. Contains 370528 sequences. (Running on oeis4.)