

A072164


Numbers k >= 1 such that f(k) = k^k  (k1)^(k1) is prime.


7




OFFSET

1,1


COMMENTS

Enoch Haga proposed studying the primality of f(k) and he already knew the first 4 solutions. C. Rivera found the next four solutions using Ubasic and the last one using PRIMEFORM. Currently f(1907) is only a probable prime number, according to PRIMEFORM.


LINKS



EXAMPLE

2^2  1^1 = 3 is prime.


MATHEMATICA

Select[Range[2, 200], PrimeQ[ #^#(#1)^(#1)]&] (* T. D. Noe, Jun 12 2008 *)


PROG

(PARI) isok(k) = ispseudoprime(k^k  (k1)^(k1)); \\ Jinyuan Wang, Mar 19 2020


CROSSREFS



KEYWORD

nonn,hard,more


AUTHOR



EXTENSIONS



STATUS

approved



