

A087575


Smallest prime p such that 2+p^n is a prime, or 0 if no such prime exists.


0



3, 3, 3, 3, 11, 0, 53, 3, 11, 3, 23, 0, 71, 3, 3, 0, 5, 0, 521, 0, 1847, 0, 41, 3, 71, 3, 59, 0, 191, 0, 71, 0, 827, 0, 761, 3, 1721, 0, 23, 0, 197, 0, 1229, 0, 59, 0, 1493, 0, 101, 0, 389, 0, 2381, 0, 3023, 0, 4691, 0, 6263, 0, 9719, 0, 3, 0, 2207, 0, 983, 0, 6701, 0, 239, 0, 347
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OFFSET

1,1


LINKS

Table of n, a(n) for n=1..73.


EXAMPLE

a(2)=a(3)=a(4)=3, as 3^2 + 2, 3^3 + 2, 3^4 + 2 are all prime.


PROG

(PARI) for(j=1, 50, forprime (i=1, 50000, if(isprime(i^j+2), print1(i, ", "); break())))


CROSSREFS

Sequence in context: A087576 A337328 A201700 * A001270 A029630 A170858
Adjacent sequences: A087572 A087573 A087574 * A087576 A087577 A087578


KEYWORD

nonn


AUTHOR

Amarnath Murthy, Sep 17 2003


EXTENSIONS

More terms from Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 14 2004
More terms from David Wasserman, Jun 08 2005


STATUS

approved



