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 A365062 #41 Aug 25 2023 08:50:57
%S A365062 1,1,2,4,7,14,28,56,112,224,448,896,1792,3584,7168,14336,28672,57344,
%T A365062 114688,229376,458752,917504,1835008,3670016,7340032,14680064,
%U A365062 29360128,58720256,117440512,234881024,469762048,939524096,1879048192,3758096384,7516192768,15032385536
%N A365062 Enumeration of | Sort_n(123,321) |.
%H A365062 Christopher Bao, Yunseo Choi, Katelyn Gan, and Owen Zhang, <a href="https://arxiv.org/abs/2308.09344">On a Conjecture by Baril, Cerbai, Khalil, and Vajnovszki on Two Restricted Stacks</a>, arXiv:2308.09344 [math.CO], 2023. See Theorems 1.1 and 1.2, pp. 2-3.
%H A365062 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (2).
%F A365062 a(0) = 1, a(n) = 2^(n-1) for n = 1..3, a(n) = 7*2^(n-4) for n > 3.
%F A365062 From _Chai Wah Wu_, Aug 24 2023: (Start)
%F A365062 a(n) = 2*a(n-1) for n > 4.
%F A365062 G.f.: (x^4 + x - 1)/(2*x - 1). (End)
%t A365062 {1}~Join~Array[If[# <= 3, 2^(# - 1), 7*2^(# - 4)] &, 30]
%Y A365062 Cf. A000079, A005009.
%K A365062 nonn,easy
%O A365062 0,3
%A A365062 _Michael De Vlieger_, Aug 23 2023