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%I #30 Jun 25 2023 01:46:23
%S 1,9,81,29,61,49,41,69,21,89,1,9,81,29,61,49,41,69,21,89,1,9,81,29,61,
%T 49,41,69,21,89,1,9,81,29,61,49,41,69,21,89,1,9,81,29,61,49,41,69,21,
%U 89,1,9,81,29,61,49,41,69,21,89
%N Final 2 digits of 9^n.
%C Period is 10, i.e., a(n+10) = a(n). - _Martin Renner_, Jun 11 2020
%H Vincenzo Librandi, <a href="/A014393/b014393.txt">Table of n, a(n) for n = 0..1000</a>
%H <a href="/index/Fi#final">Index entries for sequences related to final digits of numbers</a>
%F a(n) = 9^n mod 100. - _Martin Renner_, Jun 11 2020
%p seq(9^n mod 100, n=0..80); # _Martin Renner_, Jun 11 2020
%t Flatten[Prepend[FromDigits[Take[IntegerDigits[#],-2]]&/@(9^Range[2,60]),{1,9}]] (* _Harvey P. Dale_, Jan 22 2011 *)
%t PowerMod[9, Range[0, 80], 100] (* _Vincenzo Librandi_, Aug 16 2016 *)
%o (Magma) [Modexp(9, n, 100): n in [0..110]]; // _Vincenzo Librandi_, Aug 16 2016
%o (PARI) a(n) = lift(Mod(9, 100)^n); \\ _Michel Marcus_, Aug 16 2016
%Y Cf. A001019 (9^n), A010690 (final digit of 9^n).
%K nonn,base,easy
%O 0,2
%A _N. J. A. Sloane_
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