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A084741
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Smallest prime of the form (n^k+1)/(n+1), or 0 if no such prime exists.
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18
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3, 7, 13, 521, 31, 43, 0, 73, 9091, 13421, 19141, 157, 7027567, 211, 241, 22796593, 307, 274019342889240109297, 152381, 421, 463, 39700406579747, 183458857, 601, 135938684703251, 0, 757, 574995877
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OFFSET
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2,1
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COMMENTS
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When n is a power (greater than 2) of a prime, then (n^k+1)/(n+1) will usually be composite for all k, which is the case for n = 8, 27, 32, 64, 125. The next term, a(30), is a 204-digit number. - T. D. Noe, Jan 22 2004
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LINKS
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Table of n, a(n) for n=2..29.
H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7.
R. G. Wilson, v, Letter to N. J. A. Sloane, circa 1991.
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EXAMPLE
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a(7)= 43 = (7^3 +1 )/(7+1) = 1 - 7 + 7^2 is a prime.
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CROSSREFS
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Cf. A084742 (least k such that (n^k+1)/(n+1) is prime).
Sequence in context: A221211 A322301 A154821 * A135623 A172291 A089305
Adjacent sequences: A084738 A084739 A084740 * A084742 A084743 A084744
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), Jun 15 2003
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EXTENSIONS
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More terms from T. D. Noe, Jan 22 2004
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STATUS
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approved
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