login
This site is supported by donations to The OEIS Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A204940 Numbers n such that (23^n - 1)/22 is prime. 1
5, 3181, 61441, 91943, 121949 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

No other terms < 100000.

LINKS

Table of n, a(n) for n=1..5.

H. Lifchitz, Mersenne and Fermat primes field

MATHEMATICA

Select[Prime[Range[100]], PrimeQ[(23^#-1)/22]&]

PROG

(PARI) is(n)=ispseudoprime((23^n-1)/22) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Cf. A028491, A004061, A004062, A004063, A004023, A004064, A016054, A006032, A006033, A006034, A006035, A127995, A127996, A127997, A127998, A127999, A128000, A098438, A128002, A128003, A128004, A128005.

Sequence in context: A171980 A013782 A137841 * A172954 A079173 A073826

Adjacent sequences:  A204937 A204938 A204939 * A204941 A204942 A204943

KEYWORD

hard,nonn,more

AUTHOR

Robert Price, Jan 20 2012

EXTENSIONS

a(5)=121949 corresponds to a probable prime discovered by Paul Bourdelais, Oct 19 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 | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 16 03:14 EST 2019. Contains 330013 sequences. (Running on oeis4.)