OFFSET
1,2
COMMENTS
Conjecture: For n > 1, k^n == 1-k (mod n) has an infinite number of positive solutions.
a(6) > 10^12. No term can be a multiple of 2, 3, 5, 7, or 13. Also terms: 228454543831049 and 4879573990210017348077958628152400091281634488825721395187. - Giovanni Resta, Oct 07 2019
PROG
(Magma) [1] cat [n: n in [1..10^8] | Modexp(9, n, n) + 8 eq n];
(PARI) isok(n) = Mod(9, n)^n==-8; \\ Michel Marcus, Oct 05 2019
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Juri-Stepan Gerasimov, Oct 04 2019
STATUS
approved