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A072883
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Least k >= 1 such that k^n+n is prime, or 0 if no such k exists.
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2
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1, 1, 2, 1, 2, 1, 16, 3, 2, 1, 32, 1, 118, 417, 2, 1, 14, 1, 22, 81, 76, 1, 12, 55, 28, 15, 0, 1, 110, 1, 232, 117, 230, 3, 12, 1, 4, 375, 2, 1, 48, 1, 46, 15, 218, 1, 78, 7, 100, 993, 28, 1, 624, 13, 252, 183, 226, 1, 104, 1, 1348, 777, 1294, 0, 1806, 1, 306, 1815, 10, 1, 30, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Because the polynomial x^n + n is reducible for n in A097792, a(27) and a(64) are 0. Although x^4+4 is reducible, the factor x^2-2x+2 is 1 for x=1. - T. D. Noe (noe(AT)sspectra.com), Aug 24 2004
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MATHEMATICA
| Table[If[MemberQ[{27, 64}, n], 0, k=1; While[ !PrimeQ[k^n+n], k++ ]; k], {n, 100}]
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PROG
| (PARI) a(n)=if(n<0, 0, s=1; while(isprime(s^n+n)==0, s++); s)
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CROSSREFS
| Cf. A097792 (n such that x^n+n is reducible).
Sequence in context: A179508 A134304 A134569 * A093101 A082469 A206566
Adjacent sequences: A072880 A072881 A072882 * A072884 A072885 A072886
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KEYWORD
| nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 13 2002
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EXTENSIONS
| More terms from T. D. Noe (noe(AT)sspectra.com), Aug 24 2004
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