This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A001218 #31 Aug 08 2025 08:33:57 %S A001218 1,3,9,27,81,43,29,87,61,83,49,47,41,23,69,7,21,63,89,67,1,3,9,27,81, %T A001218 43,29,87,61,83,49,47,41,23,69,7,21,63,89,67,1,3,9,27,81,43,29,87,61, %U A001218 83,49,47,41,23,69,7,21,63,89,67 %N A001218 a(n) = 3^n mod 100. %C A001218 Period is 20. %H A001218 Vincenzo Librandi, <a href="/A001218/b001218.txt">Table of n, a(n) for n = 0..1000</a> %H A001218 <a href="/index/Fi#final">Index entries for sequences related to final digits of numbers</a> %H A001218 <a href="/index/Rec#order_19">Index entries for linear recurrences with constant coefficients</a>, signature (1,-1,1,-1,1,-1,1,-1,1,-1,1,-1,1,-1,1,-1,1,-1,1). %t A001218 PowerMod[3, Range[0, 60], 100] (* _Vincenzo Librandi_, Aug 15 2016 *) %o A001218 (PARI) a(n)=lift(Mod(3,100)^n) \\ _Charles R Greathouse IV_, Dec 27 2012 %o A001218 (Magma) [Modexp(3, n, 100): n in [0..100]]; // _Vincenzo Librandi_, Aug 15 2016 %Y A001218 Cf. A001148, A216096, A216097. - _Zak Seidov_, Jul 27 2014 %K A001218 nonn,easy %O A001218 0,2 %A A001218 _N. J. A. Sloane_ %E A001218 Definition corrected by _Zak Seidov_, Jul 27 2014