A300976 Numbers k such that k^k - 5 is a prime.

4, 104, 124, 728

Offset: 1

Author

Seiichi Manyama, Mar 17 2018

Keywords

• nonn
• hard
• more

Comments

728^728 - 5 is a probable prime.

Next term, if it exists, is greater than 5000. - Vaclav Kotesovec, Mar 25 2018

Next term, if it exists, is greater than 31000. - Robert Price, Mar 26 2018

Crossrefs

Numbers k such that k^k + b is a prime: A300981 (b=-10), this sequence (b=-5), A100408 (b=-2), A100407 (b=2), A166852 (b=3), A100837 (b=4), A100838 (b=7), A300292 (b=9), A100839 (b=10), A173974 (b=43).

Programs

Mathematica

Select[Range[1000], PrimeQ[#^# - 5] &] (* Vaclav Kotesovec, Mar 25 2018 *)

PARI

isok(k) = ispseudoprime(k^k - 5); \\ Altug Alkan, Mar 17 2018