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A210669
Number of equivalence classes of S_n under transformations of positionally adjacent elements of the form abc <--> acb <--> cba where a<b<c.
6
1, 1, 2, 4, 8, 14, 27, 68, 159, 496
OFFSET
0,3
COMMENTS
Also number of equivalence classes of S_n under transformations of positionally adjacent elements of the form abc <--> bac <--> cba where a<b<c.
EXAMPLE
From Alois P. Heinz, May 19 2012: (Start)
a(3) = 4: {123, 132, 321}, {213}, {231}, {312}.
a(4) = 8: {1234, 1243, 1324, 1342, 1423, 1432, 3214, 4213, 4312}, {2134, 2143, 2341, 2431, 4123, 4132, 4321}, {2314}, {2413}, {3124, 3142, 3421}, {3241}, {3412}, {4231}. (End)
CROSSREFS
KEYWORD
nonn
AUTHOR
Tom Roby, May 08 2012
EXTENSIONS
Definition improved and comment added by Tom Roby, May 15 2012
STATUS
approved