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%I #25 Dec 07 2019 12:18:23
%S 1,3,9,8,5,15,7,2,6,18,16,10,11,14,4,12,17,13,1,3,9,8,5,15,7,2,6,18,
%T 16,10,11,14,4,12,17,13,1,3,9,8,5,15,7,2,6,18,16,10,11,14,4,12,17,13,
%U 1,3,9,8,5,15,7,2,6,18,16,10,11,14,4,12,17,13,1,3,9
%N a(n) = 3^n mod 19.
%H G. C. Greubel, <a href="/A070342/b070342.txt">Table of n, a(n) for n = 0..1000</a>
%H <a href="/index/Rec#order_10">Index entries for linear recurrences with constant coefficients</a>, signature (1, 0, 0, 0, 0, 0, 0, 0, -1, 1).
%F From _R. J. Mathar_, Apr 13 2010: (Start)
%F a(n)= a(n-1) - a(n-9) + a(n-10).
%F G.f.: (1+2*x+6*x^2-x^3-3*x^4+10*x^5-8*x^6-5*x^7+4*x^8+13*x^9)/ ((1-x) * (1+x) * (x^2 -x+1) * (x^6-x^3+1)). (End)
%F a(n) = a(n-18). - _G. C. Greubel_, Mar 12 2016
%t PowerMod[3, Range[0, 50], 19] (* _G. C. Greubel_, Mar 12 2016 *)
%o (Sage) [power_mod(3,n,19)for n in range(0, 75)] # _Zerinvary Lajos_, Nov 25 2009
%o (PARI) a(n)=lift(Mod(3,19)^n) \\ _Charles R Greathouse IV_, Mar 22 2016
%K nonn,easy
%O 0,2
%A _N. J. A. Sloane_, May 12 2002
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