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%I #6 Feb 24 2019 15:37:14
%S 0,0,0,2,6,24,100,480,1890,8960,47040,288000,1584000,10644480,
%T 74131200,615014400,3783780000,29520691200,230015385600,2199674880000,
%U 17239951872000,172890685440000,1660143513600000,19778694414336000,174145223476224000,2007117934991769600
%N Number of defective (binary) heaps on n elements where two ancestor-successor pairs do not have the correct order.
%C Or number of permutations p of [n] having exactly two pairs (i,j) in {1,...,n} X {1,...,floor(log_2(i))} such that p(i) > p(floor(i/2^j)).
%H Alois P. Heinz, <a href="/A324063/b324063.txt">Table of n, a(n) for n = 0..200</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Heap.html">Heap</a>
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Binary_heap">Binary heap</a>
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Permutation">Permutation</a>
%Y Column k=2 of A306393.
%Y Cf. A056971.
%K nonn
%O 0,4
%A _Alois P. Heinz_, Feb 13 2019
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