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 A323960 #7 Feb 16 2025 08:33:57
%S A323960 0,8,90,1200,12502,111776,1017060,8762880,77887920,705522048,
%T A323960 6268548000,60169824000,543692724960,5645713615360,52992483226560,
%U A323960 596317674101760,5840267078534400,70071467744931840,725037082634304000,9448088175337574400,100728713738898432000
%N A323960 Number of defective (binary) heaps on n elements with exactly four defects.
%C A323960 Or number of permutations p of [n] having exactly four indices i in {1,...,n} such that p(i) > p(floor(i/2)).
%H A323960 Alois P. Heinz, <a href="/A323960/b323960.txt">Table of n, a(n) for n = 4..200</a>
%H A323960 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Heap.html">Heap</a>
%H A323960 Wikipedia, <a href="https://en.wikipedia.org/wiki/Binary_heap">Binary heap</a>
%Y A323960 Column k=4 of A306343.
%Y A323960 Cf. A056971.
%K A323960 nonn
%O A323960 4,2
%A A323960 _Alois P. Heinz_, Feb 09 2019