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a(n) = 7^n mod 3*n.
1

%I #16 Sep 08 2022 08:45:57

%S 1,1,1,1,7,1,7,1,1,19,7,1,7,7,28,1,7,1,7,1,28,49,7,1,7,49,1,49,7,19,7,

%T 1,46,49,28,1,7,49,109,1,7,91,7,25,82,49,7,1,49,49,37,61,7,1,43,49,1,

%U 49,7,1,7,49,28,1,37,37,7,157,136,49,7,1,7,49

%N a(n) = 7^n mod 3*n.

%H Vincenzo Librandi, <a href="/A191562/b191562.txt">Table of n, a(n) for n = 1..1000</a>

%t Table[PowerMod[7, n, 3 n], {n, 100}] (* _Vincenzo Librandi_, Jun 12 2016 *)

%o (Magma) [Modexp(7, n, 3*n): n in [1..100]]; // _Vincenzo Librandi_, Jun 12 2016

%o (PARI) a(n)=lift(Mod(7,3*n)^n) \\ _Charles R Greathouse IV_, Dec 27 2011

%Y Cf. A083528, A083529, A083530.

%K nonn,easy

%O 1,5

%A _Vincenzo Librandi_, Jul 31 2011