OFFSET
0,5
COMMENTS
Or number of binary max heaps on [n] that give a min heap when reversed.
LINKS
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
KEYWORD
nonn,more
AUTHOR
Alois P. Heinz, May 29 2016
STATUS
approved