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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A103056 Numbers n such that 7*10^n + 3*R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
 0, 1, 2, 5, 7, 85, 345, 1595, 2105, 6386, 9119, 9332, 14707, 72560 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Also numbers n such that (22*10^n+17)/3 is prime. a(15) > 10^5. - Robert Price, Sep 26 2015 LINKS Table of n, a(n) for n=1..14. Makoto Kamada, Prime numbers of the form 733...339. Index entries for primes involving repunits. FORMULA a(n) = A101138(n-1) + 1 for n>1. EXAMPLE For n=0, (22*10^n+17)/3 = 13 which is a prime so 0 is a term. MATHEMATICA Do[ If[ PrimeQ[(22*10^n + 17)/3], Print[n]], {n, 0, 10000}] CROSSREFS Cf. A002275, A101138. Sequence in context: A293592 A042257 A343833 * A041445 A265815 A041961 Adjacent sequences: A103053 A103054 A103055 * A103057 A103058 A103059 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 19 2005 EXTENSIONS a(13) from Kamada data by Robert Price, Dec 14 2010 Inserted a(1) = 0 by Robert Price, Sep 26 2015 a(14) from Robert Price, Sep 26 2015 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 June 19 17:03 EDT 2024. Contains 373504 sequences. (Running on oeis4.)