A087576 Smallest number k > 1 such that k^n+2 is prime.

3, 3, 3, 3, 9, 39, 9, 3, 11, 3, 15, 9, 9, 3, 3, 15, 5, 9, 63, 15, 27, 39, 41, 3, 51, 3, 59, 75, 119, 99, 71, 141, 209, 87, 65, 3, 275, 45, 23, 21, 27, 27, 69, 477, 59, 147, 231, 1605, 9, 291, 65, 15, 75, 57, 9, 225, 119, 273, 855, 33, 77, 513, 3, 219, 75, 51, 489, 369

Offset

1,1

Comments

Some of the results were computed using the PrimeFormGW (PFGW) primality-testing program. - Hugo Pfoertner, Nov 16 2019

Links

Hugo Pfoertner, Table of n, a(n) for n = 1..1000

Mathematica

Table[k = 2; While[p = k^n + 2; ! PrimeQ[p], k++]; k, {n, 68}] (* T. D. Noe, Apr 03 2012 *)

Prog

(PARI) for(n=1, 68, forstep(k=3, oo, 2, if(isprime(k^n+2), print1(k, ", "); break))) \\ Hugo Pfoertner, Oct 30 2018

Crossrefs

Cf. A095302 (corresponding primes), A095303 (smallest k such that k^n-2 is prime), A095304 (corresponding primes).

Sequence in context: A365345 A111575 A161836 * A337328 A201700 A087575

Adjacent sequences: A087573 A087574 A087575 * A087577 A087578 A087579

Keyword

nonn

Author

Amarnath Murthy, Sep 17 2003

Extensions

Corrected and extended by Hugo Pfoertner, computed using PFGW, Jun 01 2004

a(49) corrected by T. D. Noe, Apr 03 2012

Status

approved