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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A102959 Numbers n such that 2*10^n + 7*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
 1, 4, 34, 36, 42, 52, 163, 208, 216, 1417, 14646, 22794, 25648, 32515, 51421 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers n such that (25*10^n+11)/9 is prime. a(16) > 10^5. - Robert Price, Mar 12 2015 LINKS Table of n, a(n) for n=1..15. Makoto Kamada, Prime numbers of the form 277...779. Index entries for primes involving repunits. FORMULA a(n) = A101968(n) + 1. MATHEMATICA Do[ If[ PrimeQ[(25*10^n + 11)/9], Print[n]], {n, 0, 10000}] CROSSREFS Cf. A002275, A101968. Sequence in context: A113086 A058153 A020197 * A057959 A220168 A227397 Adjacent sequences: A102956 A102957 A102958 * A102960 A102961 A102962 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Dec 17 2004 EXTENSIONS a(11)-a(13) from Kamada data by Robert Price, Dec 14 2010 a(14) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013 a(15) from Robert Price, Mar 12 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 August 11 04:26 EDT 2024. Contains 375059 sequences. (Running on oeis4.)