A323959 - OEIS

%I #6 Feb 09 2019 21:15:57

%S 0,3,28,250,1760,12502,82880,576060,4200960,29987760,239978112,

%T 1744142400,15361632000,119854864800,1159352230400,9698664271680,

%U 103688467983360,906866458156800,10282952826685440,97685444140416000,1224926383944806400,11906083013106585600

%N Number of defective (binary) heaps on n elements with exactly three defects.

%C Or number of permutations p of [n] having exactly three indices i in {1,...,n} such that p(i) > p(floor(i/2)).

%H Alois P. Heinz, <a href="/A323959/b323959.txt">Table of n, a(n) for n = 3..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>

%Y Column k=3 of A306343.

%Y Cf. A056971.

%K nonn

%O 3,2

%A _Alois P. Heinz_, Feb 09 2019