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 A323961 #7 Feb 16 2025 08:33:57
%S A323961 0,20,360,5922,82880,1017060,11165280,123760560,1310267904,
%T A323961 14197154400,153775564800,1646888944800,18660402342400,
%U A323961 201542310930240,2419644394552320,26818494698361600,342175409500446720,3913572812111424000,53353484649907200000
%N A323961 Number of defective (binary) heaps on n elements with exactly five defects.
%C A323961 Or number of permutations p of [n] having exactly five indices i in {1,...,n} such that p(i) > p(floor(i/2)).
%H A323961 Alois P. Heinz, <a href="/A323961/b323961.txt">Table of n, a(n) for n = 5..200</a>
%H A323961 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Heap.html">Heap</a>
%H A323961 Wikipedia, <a href="https://en.wikipedia.org/wiki/Binary_heap">Binary heap</a>
%Y A323961 Column k=5 of A306343.
%Y A323961 Cf. A056971.
%K A323961 nonn
%O A323961 5,2
%A A323961 _Alois P. Heinz_, Feb 09 2019