OFFSET
1,2
COMMENTS
a(14) > 6*10^12. - Giovanni Resta, Mar 29 2020
MATHEMATICA
Select[Range[100000], Divisible[PowerMod[13, #, #] + 2, #] &] (* Jinyuan Wang, Mar 28 2020 *)
PROG
(PARI) for(k=1, 1e6, if(Mod(13, k)^k==-2, print1(k", ")))
CROSSREFS
Solutions to 13^k == m (mod k): this sequence (m = -2), A015963 (m = -1), A116621 (m = 1), A116622 (m = 2), A116629 (m = 3), A116630 (m = 4), A116611 (m = 5), A116631 (m = 6), A116632 (m = 7), A295532 (m = 8), A116636 (m = 9), A116620 (m = 10), A116638 (m = 11), A116639 (k = 15).
KEYWORD
nonn,more
AUTHOR
Seiichi Manyama, Mar 20 2020
EXTENSIONS
a(13) from Giovanni Resta, Mar 29 2020
STATUS
approved