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

Author

Amarnath Murthy, Sep 17 2003

Keywords

• nonn

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

Crossrefs

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

Programs

Mathematica

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

PARI

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

Extensions

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

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