login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A203094 Number of nX1 0..3 arrays with every nonzero element less than or equal to some horizontal or vertical neighbor. 8
1, 4, 16, 50, 144, 422, 1268, 3823, 11472, 34350, 102896, 308419, 924532, 2771101, 8305373, 24892609, 74608516, 223618304, 670231838, 2008825312, 6020872062, 18045827096, 54087163859, 162110668160, 485879938474, 1456284886944 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

T. Mansour, M. Shattuck, Counting Peaks and Valleys in a Partition of a Set , J. Int. Seq. 13 (2010), 10.6.8, Lemma 2.1, k=4, no peak.

FORMULA

Empirical: a(n) = 4*a(n-1) -6*a(n-2) +10*a(n-3) -5*a(n-4) +6*a(n-5) -a(n-6) +a(n-7).

Empirical: G.f.: -x*(1+6*x^2+5*x^4+x^6) / ( -1+4*x-6*x^2+10*x^3-5*x^4+6*x^5-x^6+x^7 ). - R. J. Mathar, May 17 2014

EXAMPLE

Some solutions for n=5

..3....1....1....1....1....3....3....1....0....1....1....3....2....0....3....3

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

..1....3....1....2....3....3....1....0....3....0....2....3....3....3....3....0

..3....3....2....1....3....3....3....0....3....0....2....3....3....3....2....1

..3....0....2....0....3....0....3....0....0....0....1....0....1....3....1....1

CROSSREFS

Column 1 of A203101. Also a column of A228461. Cf. A217883, A217954.

Sequence in context: A217950 A217949 A227675 * A298173 A323932 A121184

Adjacent sequences:  A203091 A203092 A203093 * A203095 A203096 A203097

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 29 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 | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 7 04:20 EDT 2020. Contains 333292 sequences. (Running on oeis4.)