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 A155980 #18 Nov 07 2023 05:04:39
%S A155980 0,2,-2,3,-1,5,3,13,19,45,83,173,339,685,1363,2733,5459,10925,21843,
%T A155980 43693,87379,174765,349523,699053,1398099,2796205,5592403,11184813,
%U A155980 22369619,44739245,89478483,178956973,357913939,715827885,1431655763,2863311533,5726623059
%N A155980 First differences of A135351.
%H A155980 Paolo Xausa, <a href="/A155980/b155980.txt">Table of n, a(n) for n = 0..1000</a>
%H A155980 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (1,2).
%F A155980 G.f.: (x^2-4*x+2)*x/((1-2*x)*(x+1)). - _Alois P. Heinz_, Jan 21 2021
%t A155980 LinearRecurrence[{1,2},{0,2,-2,3},50] (* _Paolo Xausa_, Nov 07 2023 *)
%Y A155980 Cf. A135351.
%K A155980 sign,easy
%O A155980 0,2
%A A155980 _Paul Curtz_, Feb 01 2009
%E A155980 More terms from _Alois P. Heinz_, Jan 21 2021