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 A279780 #19 Jul 16 2017 16:34:47
%S A279780 1,-3,5,-9,17,-30,52,-90,154,-262,446,-758,1286,-2182,3702,-6278,
%T A279780 10646,-18054,30614,-51910,88022,-149254,253078,-429126,727638,
%U A279780 -1233798,2092054,-3547334,6014934,-10199046,17293718,-29323590,49721686,-84309126,142956310
%N A279780 Coefficients in the expansion of 1/([r] + [2r]x + [3r]x^2 + ...); [ ] = floor, r = 8/5.
%C A279780 If n > 4, then a(n) is even.
%H A279780 Clark Kimberling, <a href="/A279780/b279780.txt">Table of n, a(n) for n = 0..1000</a>
%H A279780 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (-2,-1,-2,-2).
%F A279780 G.f.: 1/([r] + [2r]x + [3r]x^2 + ...); [ ] = floor, r = 8/5.
%F A279780 G.f.: (1 - x) (1 - x^5)/(1 + 2 x + x^2 + 2 x^3 + 2 x^4).
%t A279780 z = 50; f[x_] := f[x] = Sum[Floor[(8/5)*(k + 1)] x^k, {k, 0, z}]; f[x]
%t A279780 CoefficientList[Series[1/f[x], {x, 0, z}], x]
%Y A279780 Cf. A279634, A279778, A279779, A279781, A289260.
%K A279780 sign,easy
%O A279780 0,2
%A A279780 _Clark Kimberling_, Dec 18 2016