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There are three equivalent descriptions: 1. Number of (horizontally or vertically) connected arrays of 1..n on rectangular grid (otherwise zero) with only one local maximum. 2. Number of n-polyominoes labeled 1...n such that each successive labeled cell is the neighbor of a previously labeled cell. 3. Number of connected n-step paths on a rectangular lattice, diagonal or repeated steps not allowed.
(history; published version)
#9 by Russ Cox at Sat Mar 31 12:34:49 EDT 2012
COMMENTS

Description #1 and the extended sequence are from _R. H. Hardin (rhhardin(AT)att.net), _, Oct 25 2003. The sequence was originally submitted by Joel Yellin (yellin(AT)soe.ucsc.edu), who referenced the literature on random sequential adsorption (RSA) and used description #3.

EXTENSIONS

New description and more terms from _R. H. Hardin (rhhardin(AT)att.net), _, Oct 25 2003

Discussion
Sat Mar 31
12:34
OEIS Server: https://oeis.org/edit/global/875
#8 by N. J. A. Sloane at Sat Oct 02 03:00:00 EDT 2010
COMMENTS

Description #1 and the extended sequence are from Ron R. H. Hardin (rhhardin(AT)att.net), Oct 25 2003. The sequence was originally submitted by Joel Yellin (yellin(AT)soe.ucsc.edu), who referenced the literature on random sequential adsorption (RSA) and used description #3.

KEYWORD

nonn,nice,new

EXTENSIONS

New description and more terms from Ron R. H. Hardin (rhhardin(AT)att.net), Oct 25 2003

#7 by N. J. A. Sloane at Fri Jan 09 03:00:00 EST 2009
COMMENTS

Description #1 and the extended sequence are from Ron Hardin (rhhrhhardin(AT)cadenceatt.comnet), Oct 25 2003. The sequence was originally submitted by Joel Yellin (yellin(AT)soe.ucsc.edu), who referenced the literature on random sequential adsorption (RSA) and used description #3.

KEYWORD

nonn,nice,new

EXTENSIONS

New description and more terms from Ron Hardin (rhhrhhardin(AT)cadenceatt.comnet), Oct 25 2003

#6 by N. J. A. Sloane at Fri May 11 03:00:00 EDT 2007
NAME

There are three equivalent descriptions: 1. Number of (horizontally or vertically) connected arrays of 1..n on rectangular grid (otherwise zero) with only one local maximum. 2. Number of n-polyominos polyominoes labeled 1...n such that each successive labeled cell is the neighbor of a previously labeled cell. 3. Number of connected n-step paths on a rectangular lattice, diagonal or repeated steps not allowed.

KEYWORD

nonn,nice,new

#5 by N. J. A. Sloane at Sat Jun 12 03:00:00 EDT 2004
NAME

There are three equivalent descriptions: 1. Number of arrangements (horizontally or vertically) connected arrays of 1..n on rectangular grid (otherwise zero) with only one local maximum. 2. Number of n-polyominos labeled 1...n such that each successive labeled cell is the neighbor of a previously labeled cell. 3. Number of connected n-step paths on a rectangular lattice, diagonal or repeated steps not allowed.

COMMENTS

Neighbors Description #1 and the extended sequence are considered only in x from Ron Hardin (rhh(AT)cadence.com), Oct 25 2003. The sequence was originally submitted by Joel Yellin (yellin(AT)soe.ucsc.edu), who referenced the literature on random sequential adsorption (RSA) and y directionsused description #3.

Mapping between Descriptions 1 and 3: Renumber 1..n in Description #1 as n..1, so that there is only one local minimum.

REFERENCES

Y. Fan and J. K. Percus, Use of Model Solutions in RSA on a Lattice, Phys. Rev. Lett. 67, 1677 (1991).

EXAMPLE

Examples for description #1:

.2...2.23..1.31.3113.32.1..

Examples for description #3. n=3: Place step #3 on each of six possible nearest neighbor (NN) sites of the 4 n=2 configurations given below for description #1. Total instances = 4 X 6 = 24. n=4: Place step #4 on each of 8 NN sites of 8 (straight line) configurations of the form 123. Place step #4 on each of 7 NN sites of 16 configurations of the form 12/3 (with the 3 under the 1). Total instances = 8 X 8 + 7 X 16 = 176.

KEYWORD

nonn,nice,new

AUTHOR

Joel Yellin (yellin(AT)csesoe.ucsc.edu)

EXTENSIONS

Better New description and more terms from Ron Hardin (rhh(AT)cadence.com), Oct 25 2003

Entry revised following comments from Joel Yellin (yellin(AT)soe.ucsc.edu), Mar 04, 2004

#4 by N. J. A. Sloane at Thu Feb 19 03:00:00 EST 2004
NAME

From random sequential absorption in 2 dimensions under nearest neighbor blockingNumber of arrangements of 1..n on rectangular grid (otherwise zero) with only one local maximum.

DATA

1, 1, 4, 24, 176, 1504, 14560, 156768, 1852512, 23783264, 329070176, 4874845920, 76898357216, 1285734871520, 22695759641440, 421508294003424, 8211642378316768

COMMENTS

Neighbors are considered only in x and y directions.

EXAMPLE

For n=2 there are 4 possibilities:

.................

..1..2..12..21...

..2..1...........

.................

For n=3 there are 24 possibilities:

....................

.123..132..231..321.

....................

.1..1..2..3.........

.2..3..3..2.........

.3..2..1..1.........

.........................

.12.21..1.32.3...3.1..23.

..3.3..32..1.21.12.23.1..

.........................

.31.13..1.23.2...2.1..32.

.2...2.23..1.31.31.32.1..

.........................

CROSSREFS

If the numbers are constrained to be on a line: A000079, in a square array: A087518, in an n X k array: A087783.

KEYWORD

nonn,newnice

AUTHOR

Joel Yellin [ (yellin(AT)cse.ucsc.edu ])

EXTENSIONS

Better description and more terms from Ron Hardin (rhh(AT)cadence.com), Oct 25 2003

#3 by N. J. A. Sloane at Fri May 16 03:00:00 EDT 2003
NAME

From random sequential adsorption absorption in 2 dimensions under nearest neighbor blocking.

KEYWORD

nonn,new

nonn

AUTHOR

Joel Yellin [ yellin@(AT)cse.ucsc.edu ]

#2 by N. J. A. Sloane at Sat Dec 11 03:00:00 EST 1999
REFERENCES

JPA A22 A. Baram and D. Kutasov, "On the dynamics of random sequential absorption," J. Physics A: Math. Gen. 22, L251 89-L254 (1989).

KEYWORD

nonn,new

nonn

AUTHOR

Joel Yellin [ yellin@cse.ucsc.edu ]

#1 by N. J. A. Sloane at Fri Mar 15 03:00:00 EST 1996
NAME

From random sequential adsorption in 2 dimensions under nearest neighbor blocking.

DATA

1, 1, 4, 24, 176, 1504, 14560, 156768, 1852512, 23783264, 329070176

OFFSET

0,3

REFERENCES

JPA A22 L251 89.

KEYWORD

nonn

AUTHOR

Joel Yellin [yellin@cse.ucsc.edu]

STATUS

approved