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 A167434 #29 Jun 24 2024 05:35:08
%S A167434 1,-4,5,-6,13,-16,25,-42,57,-92,141,-206,325,-488,737,-1138,1713,
%T A167434 -2612,3989,-6038,9213,-14016,21289,-32442,49321,-75020,114205,
%U A167434 -173662,264245,-402072,611569,-930562,1415713,-2153700,3276837,-4985126,7584237
%N A167434 Diagonal sums of the Riordan array (1-4*x+4*x^2, x*(1-2*x)) (A167431).
%H A167434 G. C. Greubel, <a href="/A167434/b167434.txt">Table of n, a(n) for n = 0..1000</a>
%H A167434 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (0,1,-2)
%F A167434 G.f.: (1-2*x)^2/(1-x^2+2*x^3).
%F A167434 a(n) = (-1)^n*A052947(n+4). - _R. J. Mathar_, Jun 24 2024
%t A167434 LinearRecurrence[{0, 1, -2}, {1, -4, 5}, 100] (* _G. C. Greubel_, Jun 13 2016 *)
%t A167434 CoefficientList[Series[(1-4x+4x^2)/(1-x^2+2x^3),{x,0,40}],x] (* _Harvey P. Dale_, Nov 08 2022 *)
%o A167434 (PARI) x='x+O('x^40); Vec((1-4*x+4*x^2)/(1-x^2+2*x^3)) \\ _G. C. Greubel_, Jun 27 2018
%o A167434 (Magma) I:=[1,-4,5]; [n le 3 select I[n] else Self(n-2) - 2*Self(n-3): n in [1..40]]; // _G. C. Greubel_, Jun 27 2018
%Y A167434 Cf. A052947, A159287.
%K A167434 easy,sign
%O A167434 0,2
%A A167434 _Paul Barry_, Nov 03 2009