%I #7 Aug 28 2017 16:00:03
%S 1,11,21,31,41,1,11,21,31,41,1,11,21,31,41,1,11,21,31,41,1,11,21,31,
%T 41,1,11,21,31,41,1,11,21,31,41,1,11,21,31,41,1,11,21,31,41,1,11,21,
%U 31,41,1,11,21,31,41,1,11,21,31,41,1,11,21,31,41,1,11,21,31,41,1,11,21,31,41
%N 11^n mod 50.
%C An example of a sequence which is both in arithmetic and geometric progression.
%D E. Schmid, Problem 961, Math. Mag., 50 (No. 1, 1977), 52.
%t PowerMod[11,Range[0,120],50] (* or *) PadRight[{},120,{1,11,21,31,41}] (* _Harvey P. Dale_, Aug 28 2017 *)
%o (PARI) a(n)=lift(Mod(11,50)^n) \\ _Charles R Greathouse IV_, Mar 22 2016
%K nonn,easy
%O 0,2
%A _N. J. A. Sloane_, Jul 31 2005