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 A167423 #29 Sep 08 2022 08:45:48
%S A167423 1,-1,-11,-50,-186,-631,-2029,-6299,-19075,-56704,-166164,-481391,
%T A167423 -1381691,-3935125,-11134331,-31328366,-87721614,-244588519,
%U A167423 -679429225,-1881102959,-5192705779,-14296088956,-39263958696,-107601905375,-294291714551,-803416991401
%N A167423 Hankel transform of a simple Catalan convolution.
%C A167423 Hankel transform of A167422.
%H A167423 G. C. Greubel, <a href="/A167423/b167423.txt">Table of n, a(n) for n = 0..500</a>
%H A167423 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (6,-11,6,-1).
%F A167423 G.f.: ( 1-7*x+6*x^2-x^3 ) / (x^2-3*x+1)^2 .
%F A167423 a(n) = F(2*n)*(1-3*n)/2 + L(2*n)*(1-n)/2. - _Paul Barry_, Feb 22 2010
%F A167423 a(n) = 3*A001871(n-1) - 2*A001871(n) + F(2*n+4). - _Ralf Stephan_, May 21 2014
%F A167423 a(n) = 1 - Sum_{k=1..n} k*F(2*k+1), where F(n) = A000045(n). - _Vladimir Reshetnikov_, Oct 28 2015
%t A167423 Table[((1-3n) Fibonacci[2n] + (1-n) LucasL[2n])/2, {n, 0, 20}] (* _Vladimir Reshetnikov_, Oct 28 2015 *)
%t A167423 LinearRecurrence[{6, -11, 6, -1}, {1, -1, -11, -50}, 50] (* _G. C. Greubel_, Jun 12 2016 *)
%o A167423 (PARI) Vec((1-7*x+6*x^2-x^3)/(1-6*x+11*x^2-6*x^3+x^4) + O(x^100)) \\ _Altug Alkan_, Oct 29 2015
%o A167423 (Magma) [Fibonacci(2*n)*(1-3*n)/2 + Lucas(2*n)*(1-n)/2: n in [0..30]]; // _Vincenzo Librandi_, Jun 13 2016
%Y A167423 Cf. A167422, A000045, A000032.
%K A167423 easy,sign
%O A167423 0,3
%A A167423 _Paul Barry_, Nov 03 2009