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Numbers k such that A007908(k) == 1 (mod k).
1

%I #17 Oct 12 2024 09:02:14

%S 1,121487,293957,13449179,549999887

%N Numbers k such that A007908(k) == 1 (mod k).

%C a(6) > 10^11. - _Jason Yuen_, Oct 12 2024

%o (Python) # See A029455 for concat_mod

%o def isok(k): return concat_mod(10, k, k)==1%k # _Jason Yuen_, Oct 12 2024

%Y Cf. A007908, A029455, A029479, A110740.

%K nonn,base,hard,more

%O 1,2

%A _Max Alekseyev_, Jun 06 2023