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

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A103058 Numbers n such that 7*10^n + 4*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
1, 2, 19, 31, 106, 26194, 39973 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Also numbers n such that (67*10^n-13)/9 is prime.
a(8) > 10^5. - Robert Price, Sep 25 2015
LINKS
FORMULA
a(n) = A101140(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[(67*10^n - 13)/9], Print[n]], {n, 0, 10000}]
CROSSREFS
Sequence in context: A090819 A254897 A059697 * A161442 A135834 A106946
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Jan 19 2005
EXTENSIONS
a(6) from Kamada data by Robert Price, Dec 14 2010
a(7) from Robert Price, Sep 25 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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 29 06:57 EDT 2024. Contains 371265 sequences. (Running on oeis4.)