

A062572


Numbers k such that 6^k  5^k is prime.


110



2, 5, 11, 13, 23, 61, 83, 421, 1039, 1511, 31237, 60413, 113177, 135647, 258413
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OFFSET

1,1


COMMENTS

The 809 and 1176digit numbers associated with the terms 1039 and 1511 have been certified prime with Primo.  Rick L. Shepherd, Nov 15 2002


LINKS

Table of n, a(n) for n=1..15.


EXAMPLE

2 is in the sequence because 6^2  5^2 = 36  25 = 11, which is prime.
3 is not in the sequence because 6^3  5^3 = 216  125 = 91 = 7 * 13, which is not prime.


MATHEMATICA

Select[Range[1000], PrimeQ[6^#  5^#] &] (* Alonso del Arte, Sep 04 2013 *)


PROG

(PARI) forprime(p=2, 1e4, if(ispseudoprime(6^n5^n), print1(p", "))) \\ Charles R Greathouse IV, Jun 10 2011


CROSSREFS

Cf. A000043, A057468, A059801, A059802, A062573A062666.
Sequence in context: A113305 A095078 A335874 * A215214 A221868 A220141
Adjacent sequences: A062569 A062570 A062571 * A062573 A062574 A062575


KEYWORD

nonn,hard,more


AUTHOR

Mike Oakes, May 18 2001, May 19 2001


EXTENSIONS

Edited by T. D. Noe, Oct 30 2008
Two more terms (31237 and 60413) found by Predrag Minovic in 2004 corresponding to probable primes with 24308 and 47011 digits. JeanLouis Charton, Oct 06 2010
Two more terms (113177 and 135647) found by JeanLouis Charton in 2009 corresponding to probable primes with 88069 and 105554 digits. JeanLouis Charton, Oct 13 2010
a(15) from JeanLouis Charton, Apr 08 2013


STATUS

approved



