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%I #32 Dec 25 2023 13:46:42
%S 1,3,9,11,1,3,9,11,1,3,9,11,1,3,9,11,1,3,9,11,1,3,9,11,1,3,9,11,1,3,9,
%T 11,1,3,9,11,1,3,9,11,1,3,9,11,1,3,9,11,1,3,9,11,1,3,9,11,1,3,9,11,1,
%U 3,9,11,1,3,9,11,1,3,9,11,1,3,9,11,1,3,9,11,1,3,9,11,1,3,9,11,1,3,9,11,1
%N a(n) = 3^n mod 16.
%H G. C. Greubel, <a href="/A070354/b070354.txt">Table of n, a(n) for n = 0..1000</a>
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,1).
%F From _R. J. Mathar_, Apr 13 2010: (Start)
%F a(n) = a(n-4).
%F G.f.: (1 + 3*x + 9*x^2 + 11*x^3)/ ((1-x) * (1+x) * (1+x^2)). (End)
%F E.g.f.: 5*cosh(x) + 7*sinh(x) - 4*cos(x) - 4*sin(x). - _G. C. Greubel_, Mar 11 2016
%t PowerMod[3, Range[0, 50], 16] (* or *) Table[Mod[3^n, 16], {n, 0, 100}] (* _G. C. Greubel_, Mar 11 2016 *)
%o (Sage) [power_mod(3, n, 16) for n in range(0, 93)] # _Zerinvary Lajos_, Nov 25 2009
%o (PARI) a(n)=lift(Mod(3,16)^n) \\ _Charles R Greathouse IV_, Mar 22 2016
%o (Magma) [Modexp(3, n, 16): n in [0..100]]; // _Bruno Berselli_, Mar 23 2016
%K nonn,easy
%O 0,2
%A _N. J. A. Sloane_, May 12 2002
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