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 A354784 #22 May 27 2024 16:20:41
%S A354784 0,0,2,2,4,8,14,26,48,88,162,298,548,1008,1854,3410,6272,11536,21218,
%T A354784 39026,71780,132024,242830,446634,821488,1510952,2779074,5111514,
%U A354784 9401540,17292128,31805182,58498850,107596160,197900192,363995202,669491554
%N A354784 First differences of A000213, also twice A000073.
%C A354784 Number of anti-palindromic compositions of n+1 of even length.
%H A354784 Paolo Xausa, <a href="/A354784/b354784.txt">Table of n, a(n) for n = 0..1000</a>
%H A354784 George E. Andrews, Matthew Just, and Greg Simay, <a href="https://arxiv.org/abs/2102.01613">Anti-palindromic compositions</a>, arXiv:2102.01613 [math.CO], 2021. Also Fib. Q., 60:2 (2022), 164-176. See Table 1.
%H A354784 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,1).
%F A354784 From _Chai Wah Wu_, Jul 12 2022: (Start)
%F A354784 a(n) = a(n-1) + a(n-2) + a(n-3) for n > 2.
%F A354784 G.f.: -2*x^2/(x^3 + x^2 + x - 1). (End)
%t A354784 LinearRecurrence[{1, 1, 1}, {0, 0, 2}, 50] (* _Paolo Xausa_, May 27 2024 *)
%Y A354784 Cf. A000213, A000073, A135491 (essentially the same sequence).
%K A354784 nonn,easy
%O A354784 0,3
%A A354784 _N. J. A. Sloane_, Jul 12 2022