A379272 - OEIS

A379272

Number of binary min-heaps on n elements from the set {0,1} that give a max-heap when reversed.

1, 2, 3, 4, 6, 8, 10, 14, 18, 22, 33, 40, 54, 74, 93, 116, 172, 204, 268, 378, 482, 584, 905, 1036, 1378, 1858, 2520, 3002, 4700, 5298, 7089, 9456, 12420, 15452, 24160, 26542, 36646, 47634, 64183, 75568, 126118, 135226, 188098, 244172, 329098, 383142, 626452, 689466, 980284, 1229296, 1691506

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OFFSET

0,2

COMMENTS

If n is odd then a(n) is even.

LINKS

Table of n, a(n) for n=0..50.

Eric Weisstein's World of Mathematics, Heap

Wikipedia, Binary heap

EXAMPLE

a(5) = 8: 00000, 00001, 00011, 00101, 00111, 01011, 01111, 11111.

a(6) = 10: 000000, 000001, 000011, 000101, 000111, 001011, 001111, 010111, 011111, 111111. Min-heaps on 6 elements from the set {0,1} that do not give a max-heap when reversed are: 000010, 000100, 000110, 001001, 001101, 010110.

a(7) = 14: 0000000, 0000001, 0000011, 0000101, 0000111, 0001011, 0001111, 0010011, 0010111, 0011011, 0011111, 0101111, 0111111, 1111111.

CROSSREFS

Cf. A056971, A091980, A273755.

Sequence in context: A053253 A095913 A376622 * A102848 A260183 A134157

Adjacent sequences: A379269 A379270 A379271 * A379273 A379274 A379275

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Feb 18 2025

STATUS

approved