A323959 Number of defective (binary) heaps on n elements with exactly three defects.

0, 3, 28, 250, 1760, 12502, 82880, 576060, 4200960, 29987760, 239978112, 1744142400, 15361632000, 119854864800, 1159352230400, 9698664271680, 103688467983360, 906866458156800, 10282952826685440, 97685444140416000, 1224926383944806400, 11906083013106585600

Offset: 3

Author

Alois P. Heinz, Feb 09 2019

Keywords

• nonn

Comments

Or number of permutations p of [n] having exactly three indices i in {1,...,n} such that p(i) > p(floor(i/2)).

Links

• Alois P. Heinz, Table of n, a(n) for n = 3..200
• Eric Weisstein's World of Mathematics, Heap
• Wikipedia, Binary heap

Crossrefs

Column k=3 of A306343.

Cf. A056971.