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#22byMichel Marcus at Mon Oct 30 04:07:21 EDT 2017
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Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Repunit.html">Repunit</a>
Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Repunit.html">Repunit</a>
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#21byMichel Marcus at Mon Oct 30 04:06:59 EDT 2017
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| LINKS
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H. Dubner and T. Granlund, <a href="httphttps://www.cs.uwaterloo.ca/journals/JIS/VOL3/DUBNER/indexdubner.html">Primes of the Form (b^n+1)/(b+1)</a>, J. Integer Sequences, 3 (2000), #P00.2.7.
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| PROG
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(PARI) isok(n) = (denominator(p=(7^n+1)/8)==1) && isprime(p); \\ Michel Marcus, Oct 30 2017
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| STATUS
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approved
editing
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#20byAlois P. Heinz at Fri Jan 09 20:59:05 EST 2015
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#19byJon E. Schoenfield at Fri Jan 09 20:56:53 EST 2015
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#18byJon E. Schoenfield at Fri Jan 09 20:56:51 EST 2015
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lst={}; Do[p=(7^n+1)/8; If[PrimeQ[p], AppendTo[lst, n]], {n, 7!}]; lst [From _ (* _Vladimir Joseph Stephan Orlovsky_, Sep 29 2008] *)
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(Other) Using PFGW v3.3.1 [From Paul Bourdelais, Feb 17 2010]
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approved
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#17byN. J. A. Sloane at Fri Nov 14 14:36:51 EST 2014
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| LINKS
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J. Brillhart et al., <a href="http://wwwdx.amsdoi.org/10.1090/online_bksconm/conm22/">022">Factorizations of b^n +- 1</a>, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
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Discussion
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| Fri Nov 14
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| OEIS Server: https://oeis.org/edit/global/2350
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#16byAlois P. Heinz at Tue Oct 01 03:22:58 EDT 2013
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#15byJon E. Schoenfield at Tue Oct 01 03:08:35 EDT 2013
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#14byJon E. Schoenfield at Tue Oct 01 03:08:32 EDT 2013
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| EXTENSIONS
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a(9)=106187 is a probable prime based on Fermat primality testing and trial factoring to 2E13. - . - _Paul Bourdelais (paul.bourdelais(AT)gd-ais.com), _, Apr 07 2008
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approved
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#13byRuss Cox at Sat Mar 31 12:38:00 EDT 2012
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| MATHEMATICA
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lst={}; Do[p=(7^n+1)/8; If[PrimeQ[p], AppendTo[lst, n]], {n, 7!}]; lst [From _Vladimir Joseph Stephan Orlovsky (4vladimir(AT)gmail.com), _, Sep 29 2008]
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Discussion
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| Sat Mar 31
| 12:38
| OEIS Server: https://oeis.org/edit/global/876
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