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

Author

Alois P. Heinz, Feb 13 2019

Keywords

• nonn

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.