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A273755
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Number of binary min heaps on [n] that give a max heap when reversed.
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1
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1, 1, 1, 1, 2, 3, 5, 11, 26, 55, 214, 547, 1802, 6579, 22446, 77170, 401150, 1509788, 7198829, 36540168
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OFFSET
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0,5
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COMMENTS
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Or number of binary max heaps on [n] that give a min heap when reversed.
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LINKS
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Eric Weisstein's World of Mathematics, Heap
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EXAMPLE
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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.
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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