login
This site is supported by donations to The OEIS Foundation.

 

Logo

The OEIS is looking to hire part-time people to help edit core sequences, upload scanned documents, process citations, fix broken links, etc. - Neil Sloane, njasloane@gmail.com

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A057172 Numbers n such that (6^n + 1)/7 is a prime. 13
3, 11, 31, 43, 47, 59, 107, 811, 2819, 4817, 9601, 33581, 38447, 41341, 131891, 196337 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..16.

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

H. Lifchitz, Mersenne and Fermat primes field

MATHEMATICA

lst={}; Do[p=(6^n+1)/7; If[PrimeQ[p], AppendTo[lst, n]], {n, 7!}]; lst (* Vladimir Joseph Stephan Orlovsky, Sep 29 2008 *)

CROSSREFS

Sequence in context: A018781 A119215 A266970 * A277167 A277049 A261148

Adjacent sequences:  A057169 A057170 A057171 * A057173 A057174 A057175

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Sep 15 2000

EXTENSIONS

a(12) was discovered by Kamil Duszenko, Jul 15 2003

a(13) was discovered by Henri Lifchitz, Sep 15 2007

a(14) was discovered by Paul Bourdelais, Oct 01 2007

a(15)=131891, a probable prime, was discovered by Paul Bourdelais, Feb 01 2010

a(16)=196337 is a probable prime discovered by Paul Bourdelais, Feb 19 2010

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified May 27 05:27 EDT 2017. Contains 287189 sequences.