A108318 Numbers k such that (k+1)*k^k - 1 is prime.

2, 3, 4, 5, 7, 11, 15, 26, 52, 116, 359, 1547, 2465

Offset: 1

Author

Ray G. Opao, Jun 30 2005

Keywords

• more
• nonn

Comments

a(14) > 15000. - Michael S. Branicky, Oct 01 2024

Examples

			15 is in the sequence because (15+1)*15^15-1 = 16*15^15-1 = 7006302246093749999, which is prime.
		

Crossrefs

Cf. A108879.

Programs

Magma

[n: n in [1..1000] |IsPrime((n+1)*n^n-1)]; // Vincenzo Librandi, Oct 23 2014

Mathematica

Select[Range[1000], PrimeQ[(# + 1) #^# - 1] &] (* Vincenzo Librandi, Oct 23 2014 *)

PARI

isok(n) = isprime((n+1)*n^n-1); \\ Michel Marcus, Oct 23 2014