A273755 Number of binary min heaps on [n] that give a max heap when reversed.

1, 1, 1, 1, 2, 3, 5, 11, 26, 55, 214, 547, 1802, 6579, 22446, 77170, 401150, 1509788, 7198829, 36540168

Offset

0,5

Comments

Or number of binary max heaps on [n] that give a min heap when reversed.

Links

Table of n, a(n) for n=0..19.

Eric Weisstein's World of Mathematics, Heap

Wikipedia, Binary heap

Example

a(4) = 2: 1234, 1324.
a(5) = 3: 12345, 12435, 13245.
a(6) = 5: 123456, 123546, 124356, 132456, 132546.
a(7) = 11: 1234567, 1234657, 1235467, 1243567, 1243657, 1245367, 1253467, 1254367, 1324567, 1324657, 1325467.

Crossrefs

Cf. A056971, A273754.

Sequence in context: A000628 A358554 A369495 * A258804 A006888 A009589

Adjacent sequences: A273752 A273753 A273754 * A273756 A273757 A273758

Keyword

nonn,more

Author

Alois P. Heinz, May 29 2016

Status

approved