A253471 Numbers k such that 3^k + k^3 is prime.

2, 56, 10112, 63880, 78296, 125330, 222748, 1839730

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