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A323960
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Number of defective (binary) heaps on n elements with exactly four defects.
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2
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0, 8, 90, 1200, 12502, 111776, 1017060, 8762880, 77887920, 705522048, 6268548000, 60169824000, 543692724960, 5645713615360, 52992483226560, 596317674101760, 5840267078534400, 70071467744931840, 725037082634304000, 9448088175337574400, 100728713738898432000
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OFFSET
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4,2
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COMMENTS
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Or number of permutations p of [n] having exactly four indices i in {1,...,n} such that p(i) > p(floor(i/2)).
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LINKS
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Eric Weisstein's World of Mathematics, Heap
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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