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 A099277 #8 Jul 02 2023 18:57:22
%S A099277 0,1,19,400,8379,175561,3678400,77070841,1614809259,33833923600,
%T A099277 708897586339,14853015389521,311204425593600,6520439922076081,
%U A099277 136618033938004099,2862458272776010000,59975005694358205899
%N A099277 Unsigned member r=-19 of the family of Chebyshev sequences S_r(n) defined in A092184.
%C A099277 ((-1)^(n+1))*a(n) = S_{-19}(n), n>=0, defined in A092184.
%H A099277 <a href="/index/Ch#Cheby">Index entries for sequences related to Chebyshev polynomials.</a>
%H A099277 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (20, 20, -1).
%F A099277 a(n)= 2*(T(n, 21/2)-(-1)^n)/23, with twice Chebyshev's polynomials of the first kind evaluated at x=21/2: 2*T(n, 21/2)=A090729(n)= ((21+sqrt(437))^n + (21-sqrt(437))^n)/2^n.
%F A099277 a(n)= 21*a(n-1)-a(n-2)+2*(-1)^(n+1), n>=2, a(0)=0, a(1)=1.
%F A099277 a(n)= 20*a(n-1) + 20*a(n-2) - a(n-3), n>=3, a(0)=0, a(1)=1, a(2)=19.
%F A099277 G.f.: x*(1-x)/((1+x)*(1-21*x+x^2)) = x*(1-x)/(1-20*x-20*x^2+x^3) (from the Stephan link, see A092184).
%K A099277 nonn,easy
%O A099277 0,3
%A A099277 _Wolfdieter Lang_, Oct 18 2004