

A242884


Least number k such that (k^kn^n)/(kn) is prime or 0 if no such number exists.


0



2, 1, 1, 3, 3, 7, 3, 0, 0, 11, 5, 0, 4, 0, 0, 7, 16, 0, 1, 0, 281, 0, 19, 0, 0, 0, 7, 0, 35, 0, 1, 0, 113, 0, 29, 91, 19, 0, 19, 0, 23, 0, 0, 0, 0, 37, 65, 0, 0, 0, 0, 0, 153, 0, 199, 0, 0, 115, 0, 0, 0, 0, 319, 0, 47, 0, 0, 0, 13, 0, 47, 0, 0, 0, 539, 0, 0, 0, 0, 0, 13, 0, 147
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OFFSET

1,1


COMMENTS

a(n) = 0 is confirmed for k <= 5000. (Which means that the zeros are at present only conjectural.  N. J. A. Sloane, May 26 2014)
If a(i) = j, then a(j) <= i for all i and j.


LINKS

Table of n, a(n) for n=1..83.


EXAMPLE

(2^21^1)/(21) = 3 is prime. Thus a(1) = 2.


PROG

(PARI) a(n)=for(k=1, 5000, if(k!=n, s=(k^kn^n)/(kn); if(floor(s)==s, if(ispseudoprime(s), return(k)))))
n=1; while(n<100, print(a(n)); n+=1)


CROSSREFS

Sequence in context: A276777 A219876 A216655 * A197219 A300508 A120013
Adjacent sequences: A242881 A242882 A242883 * A242885 A242886 A242887


KEYWORD

nonn,hard,more


AUTHOR

Derek Orr, May 25 2014


EXTENSIONS

We don't normally allow conjectural terms, except in special circumstances. This is one of those exceptions, for if we included only terms that are known for certain, not much of this sequence would remain.  N. J. A. Sloane, May 31 2014


STATUS

approved



