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 A099531 #10 Feb 21 2016 12:16:05
%S A099531 1,0,0,0,-1,3,-6,10,-14,15,-7,-20,80,-188,351,-549,702,-622,-42,1839,
%T A099531 -5471,11560,-20064,29144,-33329,21059,27730,-142182,355626,-689121,
%U A099531 1114937,-1490892,1461360,-337220,-2996465,10030587,-22226506,39921442,-60118930,72788383,-55703295,-31057776
%N A099531 Expansion of (1+x)^3/((1+x)^3+x^4).
%C A099531 Binomial transform is A099530.
%H A099531 Harvey P. Dale, <a href="/A099531/b099531.txt">Table of n, a(n) for n = 0..1000</a>
%H A099531 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (-3,-3,-1,-1).
%F A099531 a(n)=-3a(n-1)-3a(n-2)-a(n-3)-a(n-4); a(n)=sum{j=0..n, sum{k=0..floor(j/4), C(n, j)(-1)^(n-j)C(j-3k, k)(-1)^k}}.
%t A099531 CoefficientList[Series[(1+x)^3/((1+x)^3+x^4),{x,0,50}],x] (* or *) LinearRecurrence[{-3,-3,-1,-1},{1,0,0,0},50] (* _Harvey P. Dale_, Feb 21 2016 *)
%Y A099531 Cf. A099529.
%K A099531 easy,sign
%O A099531 0,6
%A A099531 _Paul Barry_, Oct 20 2004