%I #28 Dec 07 2019 12:18:23
%S 1,2,4,8,16,5,10,20,13,26,25,23,19,11,22,17,7,14,1,2,4,8,16,5,10,20,
%T 13,26,25,23,19,11,22,17,7,14,1,2,4,8,16,5,10,20,13,26,25,23,19,11,22,
%U 17,7,14,1,2,4,8,16,5,10,20,13,26,25,23,19,11,22,17,7
%N a(n) = 2^n mod 27.
%H G. C. Greubel, <a href="/A070337/b070337.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 + x + 2*x^2 + 4*x^3 + 8*x^4 - 11*x^5 + 5*x^6 + 10*x^7 - 7*x^8 + 14*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 13 2016
%t PowerMod[2,Range[0,80],27] (* _Harvey P. Dale_, Mar 30 2012 *)
%o (Sage) [power_mod(2,n,27)for n in range(0,71)] # _Zerinvary Lajos_, Nov 03 2009
%o (PARI) a(n)=lift(Mod(2,27)^n) \\ _Charles R Greathouse IV_, Mar 22 2016
%o (GAP) List([0..88],n->PowerMod(2,n,27)); # _Muniru A Asiru_, Jan 31 2019
%K nonn,easy
%O 0,2
%A _N. J. A. Sloane_, May 12 2002