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A057177
Numbers n such that (11^n + 1)/12 is a prime.
15
5, 7, 179, 229, 439, 557, 6113, 223999, 327001, 2264611
OFFSET
1,1
LINKS
J. Brillhart et al., Factorizations of b^n +- 1, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7.
Eric Weisstein's World of Mathematics, Repunit
MATHEMATICA
lst={}; Do[p=(11^n+1)/12; If[PrimeQ[p], AppendTo[lst, n]], {n, 7!}]; lst (* Vladimir Joseph Stephan Orlovsky, Sep 29 2008 *)
CROSSREFS
Sequence in context: A164372 A318088 A123536 * A297535 A211769 A265031
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Sep 15 2000
EXTENSIONS
a(8) corresponds to a probable prime discovered by Paul Bourdelais, Feb 12 2010
a(9) corresponds to a probable prime discovered by Paul Bourdelais, Sep 30 2013
a(10) by Paul Bourdelais, Jul 19 2021
STATUS
approved