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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A103107 Numbers n such that 9*10^n + 8*R_n - 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
0, 6, 9, 90, 111, 210, 237, 414, 1192, 1260, 5836, 6772, 24861, 52431 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also numbers n such that (89*10^n-71)/9 is prime.

a(15) > 10^5. - Robert Price, Nov 12 2015

LINKS

Table of n, a(n) for n=1..14.

Makoto Kamada, Prime numbers of the form 988...881.

Index entries for primes involving repunits.

FORMULA

a(n) = A101016(n-1) + 1, for n > 1.

MATHEMATICA

Do[ If[ PrimeQ[(89*10^n - 71)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101016.

Sequence in context: A299917 A204383 A266006 * A121233 A156180 A191011

Adjacent sequences:  A103104 A103105 A103106 * A103108 A103109 A103110

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 and added a(14) from Robert Price, Nov 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 | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 5 18:00 EDT 2021. Contains 346488 sequences. (Running on oeis4.)