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 A156591 #15 Feb 01 2025 19:03:34
%S A156591 2,-7,6,-8,4,-12,-4,-28,-36,-92,-164,-348,-676,-1372,-2724,-5468,
%T A156591 -10916,-21852,-43684,-87388,-174756,-349532,-699044,-1398108,
%U A156591 -2796196,-5592412,-11184804,-22369628,-44739236,-89478492,-178956964,-357913948,-715827876
%N A156591 First differences of A154570.
%H A156591 Vincenzo Librandi, <a href="/A156591/b156591.txt">Table of n, a(n) for n = 0..1000</a>
%H A156591 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (1, 2).
%F A156591 a(n)+a(n+1) = -A000079(n-1), n>0.
%F A156591 a(n+1) = 4*(-1)^(n+1)- A154879(n).
%F A156591 G.f.: (1-3*x)*(2-3*x)/((1+x)*(1-2*x)). a(n) = -2^n/6+20*(-1)^n/3, n>0. - _R. J. Mathar_, Feb 25 2009
%t A156591 LinearRecurrence[{1,2},{2,-7,6},40] (* _Harvey P. Dale_, Feb 01 2025 *)
%K A156591 sign,easy
%O A156591 0,1
%A A156591 _Paul Curtz_, Feb 10 2009
%E A156591 Edited by _R. J. Mathar_, Feb 25 2009