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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A141798 Numbers n such that 2*23^n + 1 is prime. 4
0, 1, 5, 21, 261, 47589, 93337 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Primes found and proved by PrimeForm. No more terms up to 20000.

a(6) and a(7) proved prime by the primality proving program LLR. - Robert Price, Jan 06 2016

a(8) > 2*10^5. - Robert Price, Jan 06 2016

LINKS

Table of n, a(n) for n=1..7.

MATHEMATICA

Join[{0}, Select[Range[1, 261, 2], PrimeQ[2*23^# + 1] &]] (* Arkadiusz Wesolowski, Nov 06 2012 *)

PROG

(PARI) is(n)=ispseudoprime(2*23^n+1) \\ Charles R Greathouse IV, Feb 20 2017

CROSSREFS

Cf. A141774, A141797, A141802, A190942, A068231.

Sequence in context: A119686 A241467 A267020 * A301797 A015461 A101694

Adjacent sequences:  A141795 A141796 A141797 * A141799 A141800 A141801

KEYWORD

hard,nonn

AUTHOR

Rick L. Shepherd, Jul 05 2008

EXTENSIONS

a(6)-a(7) from Robert Price, Jan 06 2016

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 October 17 18:58 EDT 2019. Contains 328127 sequences. (Running on oeis4.)