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A324064
Number of defective (binary) heaps on n elements where three ancestor-successor pairs do not have the correct order.
2
0, 0, 0, 0, 6, 24, 120, 640, 3150, 16128, 94080, 614400, 3801600, 26864640, 203174400, 1757184000, 11783772000, 95122227200, 794598604800, 7821066240000, 65767223808000, 675845406720000, 6895980748800000, 83909612666880000, 784784318782464000
OFFSET
0,5
COMMENTS
Or number of permutations p of [n] having exactly three 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=3 of A306393.
Cf. A056971.
Sequence in context: A051197 A374722 A334328 * A050212 A369833 A354074
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Feb 13 2019
STATUS
approved