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 A059140 #23 Jul 02 2023 16:12:56
%S A059140 4,15,40,93,202,423,868,1761,3550,7131,14296,28629,57298,114639,
%T A059140 229324,458697,917446,1834947,3669952,7339965,14679994,29360055,
%U A059140 58720180,117440433,234880942,469761963,939524008,1879048101,3758096290,7516192671,15032385436
%N A059140 A hierarchical sequence (S(W2{2}*c) - see A059126).
%H A059140 Jonas Wallgren, <a href="/A059126/a059126.txt">Hierarchical sequences</a>
%H A059140 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (4, -5, 2).
%F A059140 Conjectures from _Colin Barker_, Oct 07 2015: (Start)
%F A059140 a(n) = 2*(-5 + 7*2^n) - 3*n.
%F A059140 a(n) = 4*a(n-1) - 5*a(n-2) + 2*a(n-3) for n > 2.
%F A059140 G.f.: (x-4) / ((x-1)^2*(2*x-1)).
%F A059140 (End)
%Y A059140 Cf. A059126.
%K A059140 nonn
%O A059140 0,1
%A A059140 _Jonas Wallgren_, Jan 19 2001
%E A059140 More terms from _Sean A. Irvine_, Sep 13 2022