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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
OFFSET
1,1
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 A342400
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