

A240748


Numbers n such that n^k  (n1)^k  ...  3^k  2^k  1 is prime for some k.


1




OFFSET

1,1


COMMENTS

a(7) > 13. See A240747 for more information.
a(n) is also the nvalues such that A240747(n) is nonzero.
It is known that a(n) == 1 mod 4 or 2 mod 4 (except a(2) = 4).
If n is not squarefree, then n is not a member of this sequence.
It is known that 17, 22, 30, 41, 66, and 194 are members of this sequence.


LINKS

Table of n, a(n) for n=1..6.


EXAMPLE

There are primes of the form 2^k1 (A000043) so 2 is a member of this sequence.


PROG

(PARI) s(n) = for(k=1, 6000, if(ispseudoprime(n^ksum(i=1, n1, i^k)), return(k)))
n=1; while(n<200, if(s(n), print(n)); n+=1)


CROSSREFS

Cf. A000043, A240747, A240507, A240503.
Sequence in context: A127092 A128171 A233768 * A171165 A039036 A219046
Adjacent sequences: A240745 A240746 A240747 * A240749 A240750 A240751


KEYWORD

nonn,more,hard


AUTHOR

Derek Orr, Apr 11 2014


STATUS

approved



