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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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS 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

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Last modified January 18 19:59 EST 2021. Contains 340262 sequences. (Running on oeis4.)