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 A138287 #14 Dec 12 2023 08:35:46 %S A138287 0,2,8,4,6,6,4,8,2,0,0,2,8,4,6,6,4,8,2,0,0,2,8,4,6,6,4,8,2,0,0,2,8,4, %T A138287 6,6,4,8,2,0,0,2,8,4,6,6,4,8,2,0,0,2,8,4,6,6,4,8,2,0,0,2,8,4,6,6,4,8, %U A138287 2,0,0,2,8,4,6,6,4,8,2,0,0,2,8,4,6,6,4,8,2,0,0,2,8,4,6,6,4,8,2,0,0,2,8,4,6 %N A138287 Palindromic period 10: repeat 0, 2, 8, 4, 6, 6, 4, 8, 2, 0. %H A138287 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (1,-1,1,-1,1,-1,1,-1,1). %F A138287 From _Chai Wah Wu_, Jun 04 2016: (Start) %F A138287 a(n) = a(n-1) - a(n-2) + a(n-3) - a(n-4) + a(n-5) - a(n-6) + a(n-7) - a(n-8) + a(n-9) for n > 8. %F A138287 G.f.: 2*x*(1 + 3*x - x^2 + 4*x^3 - x^4 + 3*x^5 + x^6)/((1 - x)*(1 - x + x^2 - x^3 + x^4)*(1 + x + x^ 2 + x^3 + x^4)). (End) %o A138287 (PARI) a(n)=[0, 2, 8, 4, 6, 6, 4, 8, 2, 0][n%10+1] \\ _Charles R Greathouse IV_, Jul 13 2016 %Y A138287 Cf. A117616. %K A138287 nonn,easy %O A138287 0,2 %A A138287 _Paul Curtz_, May 06 2008