cp's OEIS Frontend

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.

A279781 Coefficients in the expansion of 1/([r] + [2r]x + [3r]x^2 + ...); [ ] = floor, r = 9/5.

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%I A279781 #15 Jul 07 2025 16:35:37
%S A279781 1,-3,4,-4,4,-3,-1,8,-16,24,-30,28,-12,-20,68,-128,184,-208,168,-32,
%T A279781 -224,592,-1008,1344,-1408,960,224,-2240,4928,-7744,9664,-9216,4736,
%U A279781 5120,-20608,39936,-58368,67840,-57600,16384,63488,-180224,315904,-431104,463872
%N A279781 Coefficients in the expansion of 1/([r] + [2r]x + [3r]x^2 + ...); [ ] = floor, r = 9/5.
%C A279781 If n >= 23, then 32 divides a(n).
%H A279781 Clark Kimberling, <a href="/A279781/b279781.txt">Table of n, a(n) for n = 0..1000</a>
%H A279781 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (-2,-2,-2,-2).
%F A279781 G.f.: 1/([r] + [2r]x + [3r]x^2 + ...); [ ] = floor, r = 9/5.
%F A279781 G.f.: (1 - x) (1 - x^5)/(1 + 2 x + 2 x^2 + 2 x^3 + 2 x^4).
%t A279781 z = 50; f[x_] := f[x] = Sum[Floor[(9/5)*(k + 1)] x^k, {k, 0, z}]; f[x]
%t A279781 CoefficientList[Series[1/f[x], {x, 0, z}], x]
%t A279781 LinearRecurrence[{-2,-2,-2,-2},{1,-3,4,-4,4,-3,-1},50] (* _Harvey P. Dale_, Jul 07 2025 *)
%Y A279781 Cf. A279634, A279778, A279779, A279780.
%K A279781 sign,easy
%O A279781 0,2
%A A279781 _Clark Kimberling_, Dec 18 2016