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!)
A284779 Numbers k such that (13*10^k + 161)/3 is prime. 0
1, 2, 17, 34, 52, 54, 495, 505, 572, 750, 959, 1574, 2557, 3734, 4069, 11201, 13411, 16569, 17032, 17720, 19906, 23781, 36076, 56624, 84179, 117249, 159147 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 4 followed by k-2 occurrences of the digit 3 followed by the digits 87 is prime (see Example section).
a(28) > 2*10^5.
LINKS
Makoto Kamada, Search for 43w87.
EXAMPLE
4 is in this sequence because (13*10^2 + 161)/3 = 487 is prime.
Initial terms and associated primes:
a(1) = 1, 97;
a(2) = 2, 487;
a(3) = 17, 433333333333333387;
a(4) = 34, 43333333333333333333333333333333387;
a(5) = 52, 43333333333333333333333333333333333333333333333333387; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(13*10^# + 161)/3] &]
PROG
(PARI) isok(n) = isprime((13*10^n + 161)/3); \\ Indranil Ghosh, Apr 02 2017
CROSSREFS
Sequence in context: A307690 A100294 A192453 * A018529 A342485 A342487
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Apr 02 2017
EXTENSIONS
a(26)-a(27) from Robert Price, Nov 29 2018
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 July 23 09:37 EDT 2024. Contains 374547 sequences. (Running on oeis4.)