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Positive integers n such that 13^n == 10 (mod n).
15

%I #16 Apr 10 2020 22:09:48

%S 1,3,9,74853,1275039,27181907,31261887,989255061,4813809711,

%T 3187842157567,313768710194691

%N Positive integers n such that 13^n == 10 (mod n).

%C No other terms below 10^15. - _Max Alekseyev_, Nov 06 2018

%C 9909932321420413420533943 is a term. - _Max Alekseyev_, Jun 29 2011

%t Join[{1, 3, 9}, Select[Range[2000000], PowerMod[13, #, #] == 10 &]] (* _Robert Price_, Apr 10 2020 *)

%Y Solutions to 13^n == k (mod n): A001022 (k=0), A015963 (k=-1), A116621 (k=1), A116622 (k=2), A116629 (k=3), A116630 (k=4), A116611 (k=5), A116631 (k=6), A116632 (k=7), A295532 (k=8), A116636 (k=9), this sequence (k=10), A116638 (k=11), A116639 (k=15).

%Y Cf. A116609.

%K more,nonn

%O 1,2

%A _Zak Seidov_, Feb 19 2006

%E More terms from _Ryan Propper_, Jun 12 2006

%E Terms 1,3,9 prepended and a(10)-a(11) added by _Max Alekseyev_, Jun 29 2011, Nov 06 2018