

A062587


Numbers n such that 21^n  20^n is prime.


0



2, 19, 41, 43, 337, 479, 9127, 37549, 44017, 59971, 128327, 176191, 193601
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OFFSET

1,1


COMMENTS

Terms greater than 1000 may correspond to (unproven) strong pseudoprimes 21^n  20^n.


LINKS

Table of n, a(n) for n=1..13.
Top probable primes of the form 21^p20^p


PROG

(PARI) is(n)=ispseudoprime(21^n20^n) \\ Charles R Greathouse IV, Jun 13 2017


CROSSREFS

Cf. A000043, A057468, A059801, A059802, A062572A062666.
Sequence in context: A107143 A018610 A075682 * A109946 A141067 A296251
Adjacent sequences: A062584 A062585 A062586 * A062588 A062589 A062590


KEYWORD

nonn,hard


AUTHOR

Mike Oakes, May 18 2001, May 19 2001


EXTENSIONS

a(8) from JeanLouis Charton, Feb 29 2012
a(9) and a(10) from Robert Price, May 30 2012
Edited by M. F. Hasler, Sep 16 2013
a(11) added by JeanLouis Charton, Nov 24 2014
a(12) added by JeanLouis Charton, Feb 05 2015
a(13) added by JeanLouis Charton, Feb 18 2015


STATUS

approved



