A324065 Number of defective (binary) heaps on n elements where four ancestor-successor pairs do not have the correct order.

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

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=4 of A306393.

Cf. A056971.

Sequence in context: A175115 A301812 A268633 * A151883 A009134 A009137

Adjacent sequences: A324062 A324063 A324064 * A324066 A324067 A324068

Keyword

nonn

Author

Alois P. Heinz, Feb 13 2019

Status

approved