

A005808


Numbers n such that (11^n  1)/10 is prime.
(Formerly M5032)


18



17, 19, 73, 139, 907, 1907, 2029, 4801, 5153, 10867, 20161, 293831
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OFFSET

1,1


REFERENCES

J. Brillhart et al., Factorizations of b^n + 1. Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 2nd edition, 1985; and later supplements.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

Table of n, a(n) for n=1..12.
J. Brillhart et al., Factorizations of b^n + 1, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
H. Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927930.
H. Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927930. [Annotated scanned copy]
H. Lifchitz, Mersenne and Fermat primes field
Henri & Renaud Lifchitz, PRP Records.
S. S. Wagstaff, Jr., The Cunningham Project
Eric Weisstein's World of Mathematics, Repunit.
Index to primes in various ranges, form ((k+1)^n1)/k


MATHEMATICA

lst={}; Do[If[PrimeQ[(11^n1)/10], Print[n]; AppendTo[lst, n]], {n, 10^5}]; lst (* Vladimir Joseph Stephan Orlovsky, Aug 21 2008 *)


PROG

(PARI) is(n)=ispseudoprime((11^n1)/10) \\ Charles R Greathouse IV, Apr 29 2015


CROSSREFS

Sequence in context: A119768 A232878 A226681 * A180559 A272478 A028489
Adjacent sequences: A005805 A005806 A005807 * A005809 A005810 A005811


KEYWORD

hard,nonn


AUTHOR

N. J. A. Sloane


EXTENSIONS

a(11) = 20161 was found by Kamil Duszenko on Aug 15 2003.  Alexander Adamchuk, Feb 11 2007
a(12) = 293831 corresponds to a probable prime discovered by Paul Bourdelais with PFGW v3.3.1, Mar 08 2010


STATUS

approved



