A087577 Smallest number k such that k^n + 3 is a prime.

2, 2, 2, 2, 8, 2, 2, 4, 4, 8, 10, 2, 20, 4, 2, 2, 10, 2, 124, 46, 16, 20, 190, 14, 68, 50, 152, 2, 34, 2, 34, 122, 130, 208, 374, 46, 68, 64, 10, 28, 248, 4, 106, 230, 34, 208, 52, 34, 154, 230, 116, 302, 656, 38, 2, 10, 16, 34, 140, 140, 20, 232, 140, 28, 64, 328, 2, 98, 28, 818

Offset: 1

Author

Amarnath Murthy, Sep 17 2003

Keywords

• nonn

Examples

			a(5) = 8 as 8^5 + 3= 32771 is prime, while 2^5 +3, 4^5+3 and 6^5 +3 are composite.
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..200

Crossrefs

Cf. A087576.

Programs

Mathematica

snk[n_]:=Module[{k=1},While[!PrimeQ[k^n+3],k++];k]; Array[snk,70] (* Harvey P. Dale, Mar 08 2014 *)

PARI

for(j=1,50, for (i=1,150,if(isprime(i^j+3),print1(i,",");break())))

Extensions

More terms from Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 14 2004

More terms from David Wasserman, Jun 08 2005