A324064 Number of defective (binary) heaps on n elements where three ancestor-successor pairs do not have the correct order.

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

Alois P. Heinz, Table of n, a(n) for n = 0..200

Eric Weisstein's World of Mathematics, Heap

Wikipedia, Binary heap

Wikipedia, Permutation

Crossrefs

Column k=3 of A306393.

Cf. A056971.

Sequence in context: A026982 A051197 A334328 * A050212 A369833 A354074

Adjacent sequences: A324061 A324062 A324063 * A324065 A324066 A324067

Keyword

nonn

Author

Alois P. Heinz, Feb 13 2019

Status

approved