This site is supported by donations to The OEIS Foundation.

Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 5000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A093177 Primes of the form 90*R_n + 1, where R_n is the repunit (A002275) of length n. 10
 991, 99991, 9999991, 999999999999999999999999999999991, 999999999999999999999999999999999999999999991, 999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999991 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes of the form 10^n-9 (n=3,5,7,..,) [From Vincenzo Librandi, Nov 16 2010] LINKS Makoto Kamada, Prime numbers of the form 99...991. FORMULA a(n) =  10^(A056696(n)+1) - 9 = 10^A095714(n) - 9. CROSSREFS Cf. A056696 (corresponding n), A095714. Sequence in context: A137703 A255098 A155509 * A161926 A172698 A109149 Adjacent sequences:  A093174 A093175 A093176 * A093178 A093179 A093180 KEYWORD nonn AUTHOR Rick L. Shepherd, Mar 27 2004 EXTENSIONS Edited by Ray Chandler, Feb 26 2012 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.

Last modified December 2 15:01 EST 2016. Contains 278678 sequences.