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%I #26 Sep 08 2022 08:45:49
%S 1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,
%T 3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,
%U 9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9,1,3,9
%N a(n) = 3^n mod 13.
%C Equivalently: 3^(n+3*m) mod 13. - _G. C. Greubel_, Jul 20 2016
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,1).
%F From _R. J. Mathar_, Apr 13 2010: (Start)
%F a(n) = a(n-3).
%F G.f.: (1 + 3*x + 9*x^2)/ ((1-x)*(1+x+x^2)). (End)
%t Table[Mod[3^n,13], {n,0,50}] (* _G. C. Greubel_, Jul 20 *)
%o (Sage) [power_mod(3, n, 13)for n in range(0, 93)] #
%o (PARI) a(n)=lift(Mod(3,13)^n) \\ _Charles R Greathouse IV_, Mar 22 2016
%o (Magma) [Modexp(3, n, 13): n in [0..110]]; // _Vincenzo Librandi_, Jul 21 2016
%K nonn,easy
%O 0,2
%A _Zerinvary Lajos_, Nov 25 2009
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