A327660 Least number k > n - 2 such that k*n^k + 1 is prime.

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

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

Crossrefs

Cf. A240234, A327661, A240235.

Sequence in context: A004898 A062920 A228127 * A036111 A359323 A097549

Adjacent sequences: A327657 A327658 A327659 * A327661 A327662 A327663

Keyword

nonn,hard,more

Author

Jeppe Stig Nielsen, Sep 21 2019

Status

approved