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 A084741 Smallest prime of the form (n^k+1)/(n+1), or 0 if no such prime exists. 18
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS 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 LINKS 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. EXAMPLE a(7)= 43 = (7^3 +1 )/(7+1) = 1 - 7 + 7^2 is a prime. CROSSREFS 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 KEYWORD nonn AUTHOR Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), Jun 15 2003 EXTENSIONS More terms from T. D. Noe, Jan 22 2004 STATUS approved

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Last modified January 21 05:39 EST 2020. Contains 331104 sequences. (Running on oeis4.)