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 A166515 #15 May 10 2024 10:58:44
%S A166515 0,1,2,2,4,5,8,8,12,13,18,18,24,25,32,32,40,41,50,50,60,61,72,72,84,
%T A166515 85,98,98,112,113,128,128,144,145,162,162,180,181,200,200,220,221,242,
%U A166515 242,264,265,288,288,312,313,338,338,364,365,392,392,420,421,450,450,480
%N A166515 Partial sum of A166514.
%H A166515 G. C. Greubel, <a href="/A166515/b166515.txt">Table of n, a(n) for n = 0..1000</a>
%H A166515 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,-1,1,-1,-1,1).
%F A166515 G.f.: x(1+x-x^2+x^3)/((1+x)^2*(1-x)^3*(1+x^2)).
%F A166515 a(n) = (2n^2+6n+5)/16 + (2n-1)*(-1)^n/16 - sqrt(2)*cos(Pi*n/2+Pi/4)/4.
%t A166515 CoefficientList[Series[x (1 + x - x^2 + x^3)/((1 + x)^2*(1 - x)^3*(1 + x^2)), {x, 0, 50}], x] (* _G. C. Greubel_, May 15 2016 *)
%t A166515 LinearRecurrence[{1,1,-1,1,-1,-1,1},{0,1,2,2,4,5,8},70] (* _Harvey P. Dale_, Jan 16 2017 *)
%K A166515 easy,nonn
%O A166515 0,3
%A A166515 _Paul Barry_, Oct 16 2009