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A324065
Number of defective (binary) heaps on n elements where four ancestor-successor pairs do not have the correct order.
2
0, 0, 0, 0, 3, 24, 120, 720, 4200, 24192, 151200, 1056000, 7286400, 54743040, 442041600, 3997593600, 29081052000, 244365721600, 2164235673600, 21996748800000, 197620929792000, 2090405560320000, 22475789107200000, 280198170869760000, 2772753817946112000
OFFSET
0,5
COMMENTS
Or number of permutations p of [n] having exactly four pairs (i,j) in {1,...,n} X {1,...,floor(log_2(i))} such that p(i) > p(floor(i/2^j)).
LINKS
Eric Weisstein's World of Mathematics, Heap
Wikipedia, Binary heap
Wikipedia, Permutation
CROSSREFS
Column k=4 of A306393.
Cf. A056971.
Sequence in context: A175115 A301812 A268633 * A151883 A009134 A009137
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Feb 13 2019
STATUS
approved