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 A087099 #10 Feb 02 2021 21:08:48
%S A087099 1,3,6,11,16,24,31,42,51,65,76,93,106,126,141,164,181,207,226,255,276,
%T A087099 308,331,366,391,429,456,497,526,570,601,648,681,731,766,819,856,912,
%U A087099 951,1010,1051,1113,1156,1221,1266,1334,1381,1452,1501,1575,1626
%N A087099 Partial sums of A063914.
%H A087099 G. C. Greubel, <a href="/A087099/b087099.txt">Table of n, a(n) for n = 1..1000</a>
%H A087099 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,2,0,-1).
%F A087099 From _Chai Wah Wu_, Feb 02 2021: (Start)
%F A087099 a(n) = 2*a(n-2) - a(n-4) for n > 4.
%F A087099 G.f.: x*(x^3 + x^2 + 2*x + 1)/((x - 1)^2*(x + 1)^2). (End)
%t A087099 With[{nn=50},Accumulate[Riffle[Range[1,2*nn,2],3*Range[0,nn]+2]]] (* _Harvey P. Dale_, Jul 25 2013 *)
%Y A087099 Cf. A086848, A087098, A001068.
%K A087099 easy,nonn
%O A087099 1,2
%A A087099 _Jeremy Gardiner_, Aug 10 2003