

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
(list;
graph;
refs;
listen;
history;
text;
internal format)



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



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



CROSSREFS



KEYWORD

nonn,hard,more


AUTHOR



EXTENSIONS

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


STATUS

approved



