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A323960 Number of defective (binary) heaps on n elements with exactly four defects. 2
0, 8, 90, 1200, 12502, 111776, 1017060, 8762880, 77887920, 705522048, 6268548000, 60169824000, 543692724960, 5645713615360, 52992483226560, 596317674101760, 5840267078534400, 70071467744931840, 725037082634304000, 9448088175337574400, 100728713738898432000 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,2

COMMENTS

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

LINKS

Alois P. Heinz, Table of n, a(n) for n = 4..200

Eric Weisstein's World of Mathematics, Heap

Wikipedia, Binary heap

CROSSREFS

Column k=4 of A306343.

Cf. A056971.

Sequence in context: A247728 A056784 A166769 * A187667 A331512 A092956

Adjacent sequences:  A323957 A323958 A323959 * A323961 A323962 A323963

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Feb 09 2019

STATUS

approved

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Last modified November 26 21:07 EST 2021. Contains 349344 sequences. (Running on oeis4.)