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 A071381 Numbers n such that (28^n+1)/29 is a prime. 16
 3, 19, 373, 419, 491, 1031, 83497 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS (28^1031+1)/29, a 1491-digit number, has now been certified prime with Primo. a(8) > 10^5. - Robert Price, Jul 10 2013 LINKS H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7. PROG (PARI) isok(n) = (denominator(p=(28^n+1)/29)==1) && isprime(p); \\ Michel Marcus, Oct 29 2017 CROSSREFS Cf. A071380, A071382. Sequence in context: A132876 A229832 A219270 * A195639 A195640 A195641 Adjacent sequences:  A071378 A071379 A071380 * A071382 A071383 A071384 KEYWORD nonn,more AUTHOR Rick L. Shepherd, May 22 2002 EXTENSIONS a(7) from Robert Price, Jul 10 2013 STATUS approved

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Last modified December 6 21:48 EST 2019. Contains 329809 sequences. (Running on oeis4.)