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%I #22 Feb 21 2024 02:18:40
%S 10,50,500,5000,50000,500000,5000000,50000000,500000000,5000000000,
%T 50000000000,500000000000,5000000000000,50000000000000,
%U 500000000000000,5000000000000000,50000000000000000,500000000000000000
%N Period of powers of 11 mod 10^n.
%C Essentially the same as A093143. - _R. J. Mathar_, Sep 06 2012
%C Also period of squares mod 10^n. - _Mohammed Yaseen_, Apr 18 2023
%H <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (10).
%F a(n) = 5*10^(n-1), n >= 2.
%e a(2) = 50 because 11^50 = 11739085287969531650666649599035831993898213898723001 = 1 mod 1000.
%t Join[{10}, NestList[10*# &, 50, 20]] (* _Paolo Xausa_, Feb 20 2024 *)
%Y Cf. A001020, A216099.
%K nonn,base,easy
%O 1,1
%A _V. Raman_, Sep 02 2012