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 A178008 #16 Feb 24 2025 16:48:44 %S A178008 1,1,1,2,6,12,40,180,630,3360,22680,113400,831600,7484400,38918880, %T A178008 302702400,2918916000,20432412000,205837632000,2500927228800, %U A178008 21598916976000,263986763040000,3837961401120000,33774060329856000,431557437548160000,6658314750743040000 %N A178008 Number of permutations of 1..n with no element e[i>=2]<e[1+floor((i-2)/3)] (3-way heap). %C A178008 a(n) is also the number of labeled histories for the trifurcating labeled topology that possesses the largest number of labeled histories, among all labeled topologies with 2n+1 leaves. - _Noah A Rosenberg_, Feb 24 2025 %H A178008 Alois P. Heinz, <a href="/A178008/b178008.txt">Table of n, a(n) for n = 0..502</a> %H A178008 E. H. Dickey, N. A. Rosenberg, <a href="https://doi.org/10.1098/rstb.2023.0307">Labelled histories with multifurcation and simultaneity</a>, Phil. Trans. R. Soc. B 380 (2025), 20230307. %H A178008 Wikipedia, <a href="https://en.wikipedia.org/wiki/D-ary_heap">D-ary heap</a> %Y A178008 Simple 2-way heap A056971. %Y A178008 Column k=3 of A273693. %K A178008 nonn %O A178008 0,4 %A A178008 _R. H. Hardin_, May 17 2010 %E A178008 a(0), a(21)-a(25) from _Alois P. Heinz_, May 27 2016