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 A089145 #6 Dec 11 2019 14:49:31 %S A089145 3,2,1,6,1,2,3,2,1,6,1,2,3,2,1,6,1,2,3,2,1,6,1,2,3,2,1,6,1,2,3,2,1,6, %T A089145 1,2,3,2,1,6,1,2,3,2,1,6,1,2,3,2,1,6,1,2,3,2,1,6,1,2,3,2,1,6,1,2,3,2, %U A089145 1,6,1,2,3,2,1,6,1,2,3,2,1,6,1,2,3,2,1,6,1,2,3,2,1,6,1,2,3,2,1,6,1 %N A089145 Greatest common divisor of n^2-3 and n^2+3. %H A089145 Colin Barker, <a href="/A089145/b089145.txt">Table of n, a(n) for n = 0..1000</a> %H A089145 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,1). %F A089145 From _Colin Barker_, Dec 11 2019: (Start) %F A089145 G.f.: (3 + 2*x + x^2 + 6*x^3 + x^4 + 2*x^5) / ((1 - x)*(1 + x)*(1 - x + x^2)*(1 + x + x^2)). %F A089145 a(n) = a(n-6) for n>5. %F A089145 (End) %o A089145 (PARI) g(n) = for(x=0,n,print1(gcd(x^2-3,x^2+3)",")) %o A089145 (PARI) Vec((3 + 2*x + x^2 + 6*x^3 + x^4 + 2*x^5) / ((1 - x)*(1 + x)*(1 - x + x^2)*(1 + x + x^2)) + O(x^80)) \\ _Colin Barker_, Dec 11 2019 %K A089145 easy,nonn %O A089145 0,1 %A A089145 _Cino Hilliard_, Dec 05 2003