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!)
A295625 Numbers k such that (388*10^k - 1)/9 is prime. 0
0, 1, 7, 12, 16, 18, 37, 67, 82, 90, 133, 622, 624, 1464, 1963, 4741, 4824, 13861, 18423, 61374 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
For k > 1, numbers such that the digits 43 followed by k occurrences of the digit 1 is prime (see Example section).
a(21) > 2*10^5.
LINKS
Makoto Kamada, Search for 431w.
EXAMPLE
1 is in this sequence because (388*10^1 - 1)/9 = 431 is prime.
Initial terms and primes associated:
a(1) = 0, 43;
a(2) = 1, 431;
a(3) = 7, 431111111;
a(4) = 12, 43111111111111;
a(5) = 16, 431111111111111111; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(388*10^# - 1)/9] &]
CROSSREFS
Sequence in context: A305553 A338103 A190720 * A063303 A091215 A261410
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Nov 24 2017
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 28 16:58 EDT 2024. Contains 371254 sequences. (Running on oeis4.)