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A302088
Numbers k such that 5*k^k + 4 is prime.
2
3, 5, 9, 183, 561
OFFSET
1,1
COMMENTS
a(6), if it exists, is greater than 5000. - Vaclav Kotesovec, Apr 01 2018
a(6), if it exists, is greater than 20000. - Michael S. Branicky, Sep 02 2024
MATHEMATICA
Select[Range[1, 1000], PrimeQ[5*#^# + 4] &] (* Vaclav Kotesovec, Apr 01 2018 *)
PROG
(PARI) for(n=0, 500, if(isprime(5*n^n+4), print1(n", ")))
(PARI) lista(nn) = forstep(n=1, nn, 2, if(ispseudoprime(5*n^n+4), print1(n, ", "))); \\ Altug Alkan, Apr 01 2018
CROSSREFS
Numbers k such that b*k^k + b - 1 is prime: A110932 (b=2), A160360 (b=3), A301520 (b=4), this sequence (b=5), A302090 (b=6).
Cf. A302089.
Sequence in context: A121622 A188983 A083519 * A211414 A173706 A365440
KEYWORD
nonn,more,hard
AUTHOR
Seiichi Manyama, Apr 01 2018
EXTENSIONS
a(5) from Vaclav Kotesovec, Apr 01 2018
STATUS
approved