

A059802


Numbers n such that 5^n  4^n is prime.


111



3, 43, 59, 191, 223, 349, 563, 709, 743, 1663, 5471, 17707, 19609, 35449, 36697, 45259, 91493, 246497, 265007, 289937
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OFFSET

1,1


COMMENTS

Some of the larger entries may only correspond to probable primes.
5^1663  4^1663, a 1163digit number, has been certified prime with Primo.  Rick L. Shepherd, Nov 13 2002
4 more terms found by Predrag Minovic in 2004: 35449, 36697, 45259, 91493. Corresponding numbers of decimal digits are 24778, 25651, 31635, 63951.  Alexander Adamchuk, Dec 02 2006


LINKS

Table of n, a(n) for n=1..20.


MATHEMATICA

Select[Range[1000], PrimeQ[5^#  4^#] &] (* Alonso del Arte, Sep 09 2013 *)


PROG

(PARI) forprime(p=2, 1e5, if(ispseudoprime(5^p4^p), print1(p", "))) \\ Charles R Greathouse IV, Jun 10 2011


CROSSREFS

Cf. A000043, A057468, A059801, A128335, etc.
Sequence in context: A332973 A137192 A253577 * A139854 A194578 A185632
Adjacent sequences: A059799 A059800 A059801 * A059803 A059804 A059805


KEYWORD

nonn,hard


AUTHOR

Mike Oakes, Feb 23 2001


EXTENSIONS

New term 246497 found by JeanLouis Charton in 2008 corresponding to a probable prime with 172295 digits  JeanLouis Charton, Sep 02 2009
New term a(19) = 265007 found by JeanLouis Charton, Feb 19 2013
a(20) = 289937 found by JeanLouis Charton, Mar 15 2013


STATUS

approved



