A380903 Least positive k such that n^n * k^k - 1 is a prime, or 0 if no such k exists.

2, 2, 1, 2, 3, 4, 10147, 24

Offset

0,1

Comments

a(8) > 10^5 or a(8) = 0.

a(9) = 0, a(10) = 3, a(11) = 3142, a(12) = 559, a(13) = 3558.

a(14) > 10^5 or a(14) = 0.

Links

Table of n, a(n) for n=0..7.

Formula

a(n) = A231735(n^n).

Example

The least k > 0 such that 4^4*k^k - 1 is a prime is k = 3, so a(4) = 3.

Prog

(PARI) a(n) = for(k=1, oo, if(ispseudoprime(n^n*k^k-1), return(k))) \\ Does not terminate if a(n) = 0.

Crossrefs

Cf. A228175, A231119, A231735.

Sequence in context: A072549 A239481 A200114 * A120652 A330608 A113825

Adjacent sequences: A380898 A380899 A380902 * A380906 A380907 A380909

Keyword

nonn,hard,more,new

Author

Jason Yuen, Feb 07 2025

Status

approved