The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A103060 Numbers n such that 7*10^n + 5*R_n - 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
 1, 2, 5, 7, 23, 32, 38, 47, 116, 140, 229, 247, 734, 931, 1346, 2162, 2546, 6980, 10283, 10543, 12128, 13741, 105320 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers n such that (68*10^n-41)/9 is prime. LINKS Makoto Kamada, Prime numbers of the form 755...551. FORMULA a(n) = A101143(n) + 1. - Robert Price, Oct 13 2013 MATHEMATICA Do[ If[ PrimeQ[(68*10^n - 41)/9], Print[n]], {n, 0, 10000}] CROSSREFS Cf. A000533, A002275, A101143. Sequence in context: A243394 A175552 A279756 * A256247 A243595 A103807 Adjacent sequences:  A103057 A103058 A103059 * A103061 A103062 A103063 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 19 2005 EXTENSIONS a(19)-a(22) from Kamada data by Robert Price, Dec 14 2010 a(23) from Robert Price, Oct 13 2013 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
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified April 14 05:00 EDT 2021. Contains 342941 sequences. (Running on oeis4.)