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%I #33 Sep 08 2022 08:45:05
%S 1,7,23,5,9,11,25,19,3,21,17,15,1,7,23,5,9,11,25,19,3,21,17,15,1,7,23,
%T 5,9,11,25,19,3,21,17,15,1,7,23,5,9,11,25,19,3,21,17,15,1,7,23,5,9,11,
%U 25,19,3,21,17,15,1,7,23,5,9,11,25,19,3,21,17,15,1,7,23,5,9,11,25,19,3
%N a(n) = 7^n mod 26.
%H G. C. Greubel, <a href="/A070411/b070411.txt">Table of n, a(n) for n = 0..1000</a>
%H <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,0,0,-1,1). - _R. J. Mathar_, Apr 20 2010
%F From _R. J. Mathar_, Apr 20 2010: (Start)
%F a(n) = a(n-1) - a(n-6) + a(n-7).
%F G..f: ( -1-6*x-16*x^2+18*x^3-4*x^4-2*x^5-15*x^6 ) / ( (x-1)*(x^2+1)*(x^4-x^2+1) ). (End)
%F a(n) = a(n-12). - _G. C. Greubel_, Mar 20 2016
%t PowerMod[7,Range[0,80],26] (* or *) LinearRecurrence[{1,0,0,0,0,-1,1},{1,7,23,5,9,11,25},81] (* _Harvey P. Dale_, Dec 26 2011 *)
%o (Sage) [power_mod(7,n,26)for n in range(0,81)] # _Zerinvary Lajos_, Nov 27 2009
%o (PARI) a(n) = lift(Mod(7, 26)^n); \\ _Altug Alkan_, Mar 20 2016
%o (Magma) [Modexp(7, n, 26): n in [0..100]]; // _Bruno Berselli_, Mar 22 2016
%K nonn
%O 0,2
%A _N. J. A. Sloane_, May 12 2002