%I #10 Oct 20 2016 06:03:42
%S 1,2,46,2227,6684830083,12827743861,151652531182,155657642297,
%T 3102126273955,11006109076099,50473807426174,172794904196354
%N Positive integers n such that 7^n == 3 (mod n).
%C No other terms below 10^15.
%o (PARI) isok(n) = Mod(7, n)^n == 3; \\ _Michel Marcus_, Oct 20 2016
%Y Cf. A066438, A277126.
%Y Cf. Solutions to 7^n == k (mod n): A277371 (k=-3), A277370 (k=-2), A015954 (k=-1), A067947 (k=1), A277401 (k=2).
%Y Cf. Solutions to b^n == 3 (mod n): A050259 (b=2), A130422 (b=4), A123061 (b=5), A116629 (b=13).
%K nonn,hard,more
%O 1,2
%A _Max Alekseyev_, Oct 19 2016