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

Author

Jeppe Stig Nielsen, Sep 21 2019

Keywords

• nonn
• hard
• more

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.

Examples

			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.
		

Links

• Chris K. Caldwell, The Top Twenty: Generalized Cullen.

Crossrefs

Cf. A240234, A327661, A240235.

Programs

PARI

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