login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A201347 Number of n X 2 0..1 arrays with rows and columns lexicographically nondecreasing and every element equal to at least one horizontal or vertical neighbor. 1
2, 4, 8, 14, 23, 36, 54, 78, 109, 148, 196, 254, 323, 404, 498, 606, 729, 868, 1024, 1198, 1391, 1604, 1838, 2094, 2373, 2676, 3004, 3358, 3739, 4148, 4586, 5054, 5553, 6084, 6648, 7246, 7879, 8548, 9254, 9998, 10781, 11604, 12468, 13374, 14323, 15316, 16354 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 2 of A201353.

LINKS

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

FORMULA

Empirical: a(n) = (1/6)*n^3 - (1/2)*n^2 + (10/3)*n - 2 for n>1.

Conjectures from Colin Barker, May 22 2018: (Start)

G.f.: x*(2 - 4*x + 4*x^2 - 2*x^3 + x^4) / (1 - x)^4.

a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>5.

(End)

EXAMPLE

Some solutions for n=10:

..0..0....0..0....0..0....0..0....0..1....0..1....0..0....0..0....0..0....0..0

..0..0....0..0....0..0....0..0....0..1....0..1....0..0....0..1....0..1....0..0

..0..1....0..0....0..0....0..0....1..0....0..1....0..0....0..1....0..1....0..0

..0..1....0..0....1..1....0..1....1..0....0..1....0..0....0..1....0..1....0..0

..0..1....0..0....1..1....0..1....1..0....0..1....0..0....1..0....1..0....0..0

..0..1....0..0....1..1....0..1....1..0....1..0....0..0....1..0....1..0....0..1

..0..1....0..0....1..1....1..1....1..0....1..0....0..1....1..0....1..0....0..1

..0..1....0..0....1..1....1..1....1..0....1..0....0..1....1..1....1..0....0..1

..1..0....0..1....1..1....1..1....1..1....1..0....0..1....1..1....1..0....1..0

..1..0....1..1....1..1....1..1....1..1....1..0....1..1....1..1....1..1....1..0

CROSSREFS

Cf. A201353.

Sequence in context: A261968 A138526 A286522 * A089054 A055291 A091773

Adjacent sequences:  A201344 A201345 A201346 * A201348 A201349 A201350

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 30 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 October 22 00:52 EDT 2019. Contains 328315 sequences. (Running on oeis4.)