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 A010720 #24 Dec 14 2023 06:05:39
%S A010720 5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,
%T A010720 5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,5,9,
%U A010720 5,9,5,9,5,9,5,9,5,9,5,9,5
%N A010720 Period 2: repeat (5,9).
%C A010720 Continued fraction expansion of A176324. - _R. J. Mathar_, Mar 08 2012
%H A010720 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,1).
%F A010720 a(n) = -2*(-1)^n + 7. - _Paolo P. Lava_, Oct 20 2006
%F A010720 a(n) = a(n-2) for n > 1; a(0) = 5, a(1) = 9. G.f.: (5+9*x)/((1-x)*(1+x)). - _Vincenzo Librandi_, Aug 01 2010
%t A010720 Table[5 + 4 Mod[n, 2], {n, 0, 50}] (* _Jinyuan Wang_, Feb 26 2020 *)
%o A010720 (PARI) a(n)=n%2*4+5 \\ _Charles R Greathouse IV_, Jul 13 2016
%K A010720 nonn,easy
%O A010720 0,1
%A A010720 _N. J. A. Sloane_