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 A099491 #6 Jun 13 2015 00:51:33
%S A099491 1,0,0,1,-1,-2,2,1,-4,3,6,-10,-3,19,-12,-24,43,8,-83,56,100,-187,-21,
%T A099491 354,-262,-411,820,39,-1506,1210,1673,-3593,56,6400,-5545,-6768,15705,
%U A099491 -1216,-27144,25273,27207,-68490,9442,114857,-114644,-108565,298054,-58738,-484827,517803,429452,-1294392,330499
%N A099491 A Chebyshev transform of Padovan numbers.
%C A099491 A Chebyshev transform of A000931(n+3), which has g.f. 1/(1-x^2-x^3). The image of G(x) under the Chebyshev transform is (1/(1+x^2))G(x/(1+x^2)).
%H A099491 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0,-2,1,-2,0,-1).
%F A099491 G.f.: (1+x^2)^2/(1+2x^2-x^3+2x^4+x^6); a(n)=-2a(n-2)+a(n-3)-2a(n-4)-a(n-6); a(n)=sum{k=0..floor(n/2), C(n-k, k)(-1)^k*sum{j=0..floor((n-2k)/2), C(j, n-2k-2j)}}.
%Y A099491 Cf. A099492.
%K A099491 easy,sign
%O A099491 0,6
%A A099491 _Paul Barry_, Oct 19 2004