The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A103000 Numbers n such that 4*10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 2
 0, 3, 4, 6, 10, 12, 18, 40, 48, 96, 106, 114, 144, 364, 618, 1090, 11370, 59454, 196684 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers n such that (44*10^n+1)/9 is prime. a(20) > 2*10^5. - Robert Price, Mar 30 2015 LINKS Table of n, a(n) for n=1..19. Makoto Kamada, Prime numbers of the form 488...889. Index entries for primes involving repunits. FORMULA a(n) = A101737(n-1) + 1. MATHEMATICA Do[ If[ PrimeQ[(44*10^n + 1)/9], Print[n]], {n, 0, 10000}] CROSSREFS Cf. A002275, A101737. Sequence in context: A309317 A249666 A113887 * A344516 A310001 A310002 Adjacent sequences: A102997 A102998 A102999 * A103001 A103002 A103003 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 17 2005 EXTENSIONS Addition of a(16)-a(18) from Kamada data by Robert Price, Dec 10 2010 0 added by Arkadiusz Wesolowski, Mar 10 2011 STATUS approved

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

Last modified May 29 07:13 EDT 2023. Contains 363029 sequences. (Running on oeis4.)