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 A290186 #7 Sep 12 2017 20:25:17
%S A290186 1,5,17,52,152,435,1232,3471,9753,27367,76738,215098,602811,1689212,
%T A290186 4733317,13262821,37162121,104126704,291757632,817488295,2290553580,
%U A290186 6417991803,17982818177,50386743719,141180528542,395579064834,1108387929991,3105633996920,8701793132873,24381882610741
%N A290186 Expansion of (1+x)/ ((1+x)^3-7*x).
%H A290186 T.-X. He, L. W. Shapiro, <a href="http://dx.doi.org/10.1016/j.laa.2017.06.025">Fuss-Catalan matrices, their weighted sums, and stabilizer subgroups of the Riordan group</a>, Lin. Alg. Applic. 532 (2017) 25-41, page 34, m=3.
%H A290186 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (4,-3,-1).
%F A290186 a(n) = A215404(n+2)+A215404(n+1).
%t A290186 CoefficientList[Series[(1+x)/((1+x)^3-7x),{x,0,30}],x] (* _Harvey P. Dale_, Sep 12 2017 *)
%Y A290186 Pairwise sums of A215404.
%K A290186 nonn,easy
%O A290186 0,2
%A A290186 _R. J. Mathar_, Jul 23 2017