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A323958
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Number of defective (binary) heaps on n elements with exactly two defects.
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2
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0, 2, 9, 48, 250, 1200, 5922, 34160, 185460, 1201920, 6837600, 49680576, 314028000, 2611065600, 17913619680, 162456519680, 1235053617600, 12593800627200, 99016069824000, 1062491684981760, 9425603347776000, 114292447803494400, 1026754912019865600
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OFFSET
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2,2
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COMMENTS
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Or number of permutations p of [n] having exactly two 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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