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 A227656 #42 Aug 04 2024 03:20:46
%S A227656 1,1,4,44,896,29392,1413792,93770800,8201380224,914570667792,
%T A227656 126651310675680,21323599202141616,4289517397262212416,
%U A227656 1016086393608958657680,279937626985917460931616,88754294249179769383418160,32085579878185717054048193280,13119328150439580260369558815248
%N A227656 Number of lattice paths from {2}^n to {0}^n using steps that decrement one component by 1 such that for each point (p_1,p_2,...,p_n) we have abs(p_{i}-p_{i+1}) <= 1.
%C A227656 Number of linear extensions of garland or double fence poset. - _Alexander Shashkov_, Jul 26 2020
%H A227656 Alexander Shashkov, <a href="/A227656/b227656.txt">Table of n, a(n) for n = 0..227</a> (terms 0..23 from Alois P. Heinz)
%H A227656 Oscar J. Borenstein and Alexander Shashkov, <a href="https://arxiv.org/abs/1909.04215">Garland Recurrences</a>, arXiv:1909.04215 [math.CO], 2019.
%H A227656 Jiaxi Lu and Yuanzhe Ding, <a href="https://arxiv.org/abs/2106.09471">A skeleton model to enumerate standard puzzle sequences</a>, arXiv:2106.09471 [math.CO], 2021.
%F A227656 a(n) ~ c * d^n * n^(2*n + 1/2), where d = 0.197278552664313325820060688708960349... and c = 4.4668518532326348084863454883501... - _Vaclav Kotesovec_, Dec 25 2018
%e A227656 a(2) = 2^2 = 4:
%e A227656 .
%e A227656 (1,2) (0,1)
%e A227656 / \ / \
%e A227656 (2,2) (1,1) (0,0)
%e A227656 \ / \ /
%e A227656 (2,1) (1,0)
%e A227656 .
%e A227656 a(3) = 44:
%e A227656 .
%e A227656 (1,2,2)-(1,1,2)-(0,1,2)-(0,1,1)-(0,0,1)
%e A227656 / X \ / X \
%e A227656 (2,2,2)-(2,1,2) (1,2,1)-(1,1,1)-(1,0,1) (0,1,0)-(0,0,0)
%e A227656 \ X / \ X /
%e A227656 (2,2,1)-(2,1,1)-(2,1,0)-(1,1,0)-(1,0,0)
%Y A227656 Row n=2 of A227655.
%Y A227656 Cf. A000079.
%K A227656 nonn
%O A227656 0,3
%A A227656 _Alois P. Heinz_, Jul 19 2013