A070357 - OEIS

%I #31 Dec 25 2023 11:23:53

%S 1,3,9,27,25,19,1,3,9,27,25,19,1,3,9,27,25,19,1,3,9,27,25,19,1,3,9,27,

%T 25,19,1,3,9,27,25,19,1,3,9,27,25,19,1,3,9,27,25,19,1,3,9,27,25,19,1,

%U 3,9,27,25,19,1,3,9,27,25,19,1,3,9,27,25,19,1,3,9,27,25,19,1,3,9,27,25

%N a(n) = 3^n mod 28.

%H G. C. Greubel, <a href="/A070357/b070357.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 (1,0,-1,1).

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

%F a(n) = a(n-1) - a(n-3) + a(n-4).

%F G.f.: ( -1-2*x-6*x^2-19*x^3 ) / ( (x-1)*(1+x)*(x^2-x+1) ). (End)

%F From _G. C. Greubel_, Mar 09 2016: (Start)

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

%F E.g.f.: (1/3)*( 35*cosh(x) + 49*sinh(x) - 32*exp(x/2)*cos(sqrt(3)*x/2) - 16*sqrt(3)*exp(x/2)*sin(sqrt(3)*x/2) ). (End)

%t PowerMod[3,Range[0,90],28] (* _Harvey P. Dale_, Jul 23 2012 *)

%o (Sage) [power_mod(3,n,28)for n in range(0, 83)] # _Zerinvary Lajos_, Nov 25 2009

%o (PARI) a(n)=lift(Mod(3,28)^n) \\ _Charles R Greathouse IV_, Mar 22 2016

%Y Cf. A000244.

%K nonn,easy

%O 0,2

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