A210669 - OEIS

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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.

1, 1, 2, 4, 8, 14, 27, 68, 159, 496

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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.

LINKS

Table of n, a(n) for n=0..9.

Steven Linton, James Propp, Tom Roby, and Julian West, Equivalence classes of permutations under various relations generated by constrained transpositions, 2011 arXiv:1111.3920 [math.CO], J. Int. Seq. 15 (2012) #12.9.1

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

Cf. A210667, A210668, A210671, A212417, A212418.

Sequence in context: A065616 A164147 A321402 * A122026 A196721 A118034

Adjacent sequences: A210666 A210667 A210668 * A210670 A210671 A210672

KEYWORD

nonn

AUTHOR

Tom Roby, May 08 2012

EXTENSIONS

Definition improved and comment added by Tom Roby, May 15 2012

STATUS

approved