This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A004063 Numbers n such that (7^n - 1)/6 is prime. (Formerly M3836) 19
 5, 13, 131, 149, 1699, 14221, 35201, 126037, 371669, 1264699 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Base 7 repunit primes. - Paul Bourdelais, Aug 31 2007 For Repunits with bases from -11 to 11, base 7 Repunits have the lowest relative rate of occurrence so far. - Paul Bourdelais, Feb 23 2010 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 Paul Bourdelais,A Generalized Repunit Conjecture 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), 927-930. H. Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927-930. [Annotated scanned copy] H. Lifchitz, Mersenne and Fermat primes field S. S. Wagstaff, Jr., The Cunningham Project Eric Weisstein's World of Mathematics, Repunit. MATHEMATICA For[n = 1, n <= 20000, n++, If[PrimeQ[(7^n - 1)/6 ], Print[n]]] (* Sam Handler (sam_5_5_5_0(AT)yahoo.com), Aug 09 2006 *) PROG (Prime95) PRP=1, 7, 1264699, -1, 0, 0, "6" (PARI) is(n)=isprime((7^n - 1)/6) \\ Charles R Greathouse IV, Apr 28 2015 CROSSREFS Sequence in context: A228280 A155175 A213129 * A005764 A099974 A247820 Adjacent sequences:  A004060 A004061 A004062 * A004064 A004065 A004066 KEYWORD nonn,hard AUTHOR EXTENSIONS a(6) from Robert G. Wilson v, Apr 09 2005 a(7)=35201 is a probable prime from Paul Bourdelais, Aug 31 2007 a(8)=126037 discovered Sep 17 2008 by Paul Bourdelais & Eric Purohit - it is a probable prime based on trial factoring to 2.5*10^13 and Fermat base 2 primality test. - Paul Bourdelais, Sep 18 2008 a(9)=371669 is a probable prime discovered by Paul Bourdelais, Feb 23 2010 a(10)=1264699 is a probable prime discovered by Paul Bourdelais, Jan 06 2014 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.