The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A245898

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Number of permutations avoiding 231 that can be realized on increasing unary-binary trees with n nodes.
(history; published version)

#21 by Joerg Arndt at Sun Jun 03 03:39:31 EDT 2018

STATUS

proposed

#20 by Jon E. Schoenfield at Sun Jun 03 02:26:28 EDT 2018

STATUS

editing

#19 by Jon E. Schoenfield at Sun Jun 03 02:26:25 EDT 2018

COMMENTS

In some cases, more than one tree results in the same breadth-first search reading word, but here we count the number of permutations, not the number of trees.

EXAMPLE

1 1 1 1

/ \ / \ / \ / \

2 3 2 4 3 2 4 2

| | | |

4 3 4 3

STATUS

approved

#18 by N. J. A. Sloane at Tue Aug 26 10:15:23 EDT 2014

STATUS

proposed

#17 by Manda Riehl at Fri Aug 22 14:18:57 EDT 2014

STATUS

editing

#16 by Manda Riehl at Fri Aug 22 11:09:09 EDT 2014

CROSSREFS

Cf. A245901 is the odd terms of A245898. Cf. A245888 is the number of increasing unary-binary trees whose breadth-first reading word avoids 231.

#15 by Alois P. Heinz at Sat Aug 09 21:21:58 EDT 2014

NAME

Permutations avoiding 231 that can be realized on increasing unary-binary trees.

COMMENTS

The number of permutations avoiding 231 in the classical sense which can be realized as labels on an increasing unary-binary tree read in the order they appear in a breadth-first search. (Note that breadth-first search reading word is equivalent to reading the tree left to right by levels, starting with the root.)

STATUS

reviewed

Discussion

Sat Aug 09

21:24

Alois P. Heinz: This sequence gives the number of permutations (...), it does not list the permutations.

Sun Aug 17

04:43

OEIS Server: This sequence has not been edited or commented on for a week
yet is not proposed for review.  If it is ready for review, please
visit https://oeis.org/draft/A245898 and click the button that reads
"These changes are ready for review by an OEIS Editor."

Thanks.
  - The OEIS Server

#14 by Manda Riehl at Sat Aug 09 12:25:40 EDT 2014

STATUS

proposed

Discussion

Sat Aug 09

12:29

Michel Marcus: I don't think you can click on button that says:
"I have reviewed these changes. Mark them ready for approval"
if you are actually submitting this sequence

12:31

Michel Marcus: About A245888, it's true that you haven't submitted yet.
But you're referencing it here.
Same for A245901

#13 by Manda Riehl at Tue Aug 05 22:06:36 EDT 2014

STATUS

editing

#12 by Alois P. Heinz at Tue Aug 05 21:19:56 EDT 2014

NAME

Permutations avoiding 231 that can be realized on increasing unary-binary trees

EXAMPLE

For example, when n=4, the permutations 1234, 1243, 1324, and 1423 all avoid 231 in the classical sense and occur as breadth-first search reading words on an increasing unary-binary tree with 4 nodes.

1 1 1 1

/\ /\ /\ /\

2 3 2 4 3 2 4 2

| | | |

4 3 4 3

STATUS

proposed

Discussion

Tue Aug 05

21:21

Alois P. Heinz: A245888 seems to be the same as this (reading the description).

22:06

Manda Riehl: A245888 will be very similar (but will be counting the labelled trees, not the permutations, and so the terms will be larger), but I have not submitted that one for review yet, I don't believe.