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 A099918 #20 May 10 2024 10:59:07
%S A099918 1,-1,2,-2,1,-1,0,1,-1,2,-2,1,-1,0,1,-1,2,-2,1,-1,0,1,-1,2,-2,1,-1,0,
%T A099918 1,-1,2,-2,1,-1,0,1,-1,2,-2,1,-1,0,1,-1,2,-2,1,-1,0,1,-1,2,-2,1,-1,0,
%U A099918 1,-1,2,-2,1,-1,0,1,-1,2,-2,1,-1,0,1,-1,2,-2,1
%N A099918 A Chebyshev transform related to the 7th cyclotomic polynomial.
%C A099918 The g.f. is a Chebyshev transform of 1/(1+x-2x^2-x^3) under the Chebyshev mapping g(x)->(1/(1+x^2))g(x/(1+x^2)). The denominator is the 7th cyclotomic polynomial. The inverse of the 7 cyclotomic polynomial A014016 is given by sum{k=0..n, A099918(n-k)(k/2+1)(-1)^(k/2)(1+(-1)^k)/2}.
%H A099918 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (-1,-1,-1,-1,-1,-1).
%F A099918 G.f.: (1+x^2)^2/(1+x+x^2+x^3+x^4+x^5+x^6).
%F A099918 a(n) = Sum_{k=0..floor(n/2)} C(n-k, k)^(-1)^k*b(n-2k), where b(n)=A094790(n/2+1)(1+(-1)^n)/2+A094789((n+1)/2)(1-(-1)^n)/2=(-1)^n*A006053(n+2).
%t A099918 LinearRecurrence[{-1,-1,-1,-1,-1,-1},{1,-1,2,-2,1,-1},90] (* _Harvey P. Dale_, May 25 2019 *)
%Y A099918 Cf. A099860.
%K A099918 easy,sign
%O A099918 0,3
%A A099918 _Paul Barry_, Oct 30 2004