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a(n) = 7^n mod 36.
1

%I #29 Sep 08 2022 08:45:05

%S 1,7,13,19,25,31,1,7,13,19,25,31,1,7,13,19,25,31,1,7,13,19,25,31,1,7,

%T 13,19,25,31,1,7,13,19,25,31,1,7,13,19,25,31,1,7,13,19,25,31,1,7,13,

%U 19,25,31,1,7,13,19,25,31,1,7,13,19,25,31,1,7,13,19,25,31,1,7,13,19,25,31

%N a(n) = 7^n mod 36.

%H G. C. Greubel, <a href="/A070419/b070419.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,1). [_R. J. Mathar_, Apr 20 2010]

%F From _R. J. Mathar_, Apr 20 2010: (Start)

%F a(n) = a(n-6).

%F G.f.: ( -1-7*x-13*x^2-19*x^3-25*x^4-31*x^5 ) / ( (x-1)*(1+x)*(1+x+x^2)*(x^2-x+1) ). (End)

%t PowerMod[7, Range[0, 50], 36] (* _G. C. Greubel_, Mar 20 2016 *)

%o (Sage) [power_mod(7,n,36) for n in range(0,78)] # _Zerinvary Lajos_, Nov 27 2009

%o (PARI) a(n) = lift(Mod(7, 36)^n); \\ _Altug Alkan_, Mar 20 2016

%o (Magma) [Modexp(7, n, 36): n in [0..100]]; // _Bruno Berselli_, Mar 22 2016

%K nonn,easy

%O 0,2

%A _N. J. A. Sloane_, May 12 2002