A324063 Number of defective (binary) heaps on n elements where two ancestor-successor pairs do not have the correct order.

0, 0, 0, 2, 6, 24, 100, 480, 1890, 8960, 47040, 288000, 1584000, 10644480, 74131200, 615014400, 3783780000, 29520691200, 230015385600, 2199674880000, 17239951872000, 172890685440000, 1660143513600000, 19778694414336000, 174145223476224000, 2007117934991769600

Offset

0,4

Comments

Or number of permutations p of [n] having exactly two 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=2 of A306393.

Cf. A056971.

Sequence in context: A094012 A141253 A306672 * A078486 A352364 A129817

Adjacent sequences: A324060 A324061 A324062 * A324064 A324065 A324066

Keyword

nonn

Author

Alois P. Heinz, Feb 13 2019

Status

approved