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 A324068 #7 Feb 16 2025 08:33:57
%S A324068 0,0,0,0,0,0,60,640,5040,39424,315840,2572800,22730400,207820800,
%T A324068 1979577600,20119756800,180756576000,1740900761600,17732095180800,
%U A324068 197872975872000,2123068147200000,24858537099264000,303091124244480000,4076808466857984000
%N A324068 Number of defective (binary) heaps on n elements where seven ancestor-successor pairs do not have the correct order.
%C A324068 Or number of permutations p of [n] having exactly seven pairs (i,j) in {1,...,n} X {1,...,floor(log_2(i))} such that p(i) > p(floor(i/2^j)).
%H A324068 Alois P. Heinz, <a href="/A324068/b324068.txt">Table of n, a(n) for n = 0..200</a>
%H A324068 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Heap.html">Heap</a>
%H A324068 Wikipedia, <a href="https://en.wikipedia.org/wiki/Binary_heap">Binary heap</a>
%H A324068 Wikipedia, <a href="https://en.wikipedia.org/wiki/Permutation">Permutation</a>
%Y A324068 Column k=7 of A306393.
%Y A324068 Cf. A056971.
%K A324068 nonn
%O A324068 0,7
%A A324068 _Alois P. Heinz_, Feb 13 2019