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

3,2

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.

Sequence in context: A172241 A321438 A341926 * A321385 A037777 A037665

Adjacent sequences: A323956 A323957 A323958 * A323960 A323961 A323962

Keyword

nonn

Author

Alois P. Heinz, Feb 09 2019

Status

approved