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 A010678 #20 Feb 26 2020 21:48:35
%S A010678 0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,
%T A010678 0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,0,7,
%U A010678 0,7,0,7,0,7,0,7,0,7,0,7,0
%N A010678 Period 2: repeat (0,7).
%H A010678 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,1).
%F A010678 a(n) = (7/2)*[1-(-1)^n] = 7*(n mod 2). - _Paolo P. Lava_, Oct 20 2006
%F A010678 G.f.: 7x/((1-x)(1+x)). - _R. J. Mathar_, Nov 21 2011
%t A010678 PadRight[{},120,{0,7}] (* _Harvey P. Dale_, Oct 01 2013 *)
%o A010678 (PARI) a(n)=n%2*7 \\ _Charles R Greathouse IV_, Jul 13 2016
%K A010678 nonn,easy
%O A010678 0,2
%A A010678 _N. J. A. Sloane_