

A327660


Least number k > n  2 such that k*n^k + 1 is prime.


1



1, 1, 2, 3, 1242, 91, 34, 17, 12382, 9, 10, 247
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OFFSET

1,3


COMMENTS

Different version of A240234. Some authors, like Caldwell (link), require that k + 2 > n before they use the term generalized Cullen for a prime of form k*n^k + 1.


LINKS

Table of n, a(n) for n=1..12.
Chris K. Caldwell, The Top Twenty: Generalized Cullen.


EXAMPLE

To find a(9), consider numbers k*9^k + 1 where k > 7. The first time it is prime, is for k = 12382, so a(9) = 12382.


PROG

(PARI) for(b=1, +oo, for(k=b1, +oo, if(ispseudoprime(k*b^k+1), print1(k, ", "); next(2))))


CROSSREFS

Cf. A240234, A327661, A240235.
Sequence in context: A004898 A062920 A228127 * A036111 A097549 A323518
Adjacent sequences: A327657 A327658 A327659 * A327661 A327662 A327663


KEYWORD

nonn,hard,more


AUTHOR

Jeppe Stig Nielsen, Sep 21 2019


STATUS

approved



