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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A062586 Numbers n such that 20^n - 19^n is prime. 1
5, 17, 109, 1979, 6899, 7331, 18661, 79621, 81649 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Terms n > 1000 may correspond to (unproven) strong pseudoprimes 20^n - 19^n.

LINKS

Table of n, a(n) for n=1..9.

Top probable primes of the form 20^p-19^p

PROG

(PARI) is(n)=ispseudoprime(20^n-19^n) \\ Charles R Greathouse IV, Jun 12 2017

CROSSREFS

Cf. A000043, A057468, A059801, A059802, A062572-A062666.

Sequence in context: A084167 A267143 A234797 * A067710 A197912 A203114

Adjacent sequences:  A062583 A062584 A062585 * A062587 A062588 A062589

KEYWORD

nonn,hard

AUTHOR

Mike Oakes, May 18 2001, May 19 2001

EXTENSIONS

Three more terms (18661, 79621 and 81649) found by Jean-Louis Charton in February and March 2011 corresponding to probable primes with 24279, 103590 and 106228 digits.

Edited by M. F. Hasler, Sep 16 2013

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified February 24 18:24 EST 2018. Contains 299628 sequences. (Running on oeis4.)