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a(n) = (7^n-1)/6 mod n.
3

%I #8 Feb 18 2023 08:08:15

%S 0,0,0,0,1,0,1,0,0,8,1,0,1,8,12,0,1,0,1,0,15,8,1,0,1,8,0,8,1,18,1,0,

%T 24,8,22,0,1,8,18,0,1,36,1,4,36,8,1,0,8,8,6,36,1,0,7,8,0,8,1,0,1,8,36,

%U 0,6,6,1,60,57,8,1,0,1,8,57,20,43,30,1,0,0,8,1,36,81,8,57,16,1,18,29,32,57

%N a(n) = (7^n-1)/6 mod n.

%H Antti Karttunen, <a href="/A094922/b094922.txt">Table of n, a(n) for n = 1..20000</a>

%o (PARI) A094922(n) = ((((7^n)-1)/6)%n); \\ _Antti Karttunen_, Feb 18 2023

%K nonn,look

%O 1,10

%A _N. J. A. Sloane_, Jun 18 2004