The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A202882 Number of n X 1 0..2 arrays with every nonzero element less than or equal to some horizontal or vertical neighbor. 8
1, 3, 9, 22, 51, 121, 292, 704, 1691, 4059, 9749, 23422, 56268, 135166, 324692, 779977, 1873673, 4500958, 10812237, 25973244, 62393157, 149881402, 360046432, 864906711, 2077686532, 4991036946, 11989513056, 28801314179, 69186771332 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
T. Mansour and M. Shattuck, Counting Peaks and Valleys in a Partition of a Set, J. Int. Seq. 13 (2010), 10.6.8, Lemma 2.1, k=3, one peak.
FORMULA
Empirical: a(n) = 3*a(n-1) -3*a(n-2) +4*a(n-3) -a(n-4) +a(n-5).
Empirical: G.f.: -x*(1+3*x^2+x^4)/(-1+3*x-3*x^2+4*x^3-x^4+x^5). - R. J. Mathar, Jul 09 2017
EXAMPLE
Some solutions for n=5
..2....2....1....0....2....2....0....1....0....1....1....0....2....1....0....2
..2....2....1....1....2....2....2....1....2....2....1....0....2....2....1....2
..0....1....1....2....0....2....2....0....2....2....1....1....1....2....1....0
..0....1....1....2....1....1....2....0....0....0....2....1....2....2....2....2
..0....0....1....2....1....1....1....0....0....0....2....1....2....0....2....2
CROSSREFS
Column 1 of A202889.
Sequence in context: A099166 A222083 A305612 * A350105 A336511 A054442
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 25 2011
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 24 23:50 EDT 2024. Contains 372782 sequences. (Running on oeis4.)