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!)
A207020 Number of n X 4 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 0 1 and 1 0 1 vertically. 1
9, 81, 252, 558, 1035, 1719, 2646, 3852, 5373, 7245, 9504, 12186, 15327, 18963, 23130, 27864, 33201, 39177, 45828, 53190, 61299, 70191, 79902, 90468, 101925, 114309, 127656, 142002, 157383, 173835, 191394, 210096, 229977, 251073, 273420, 297054 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 4 of A207024.

LINKS

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

FORMULA

Empirical: a(n) = 6*n^3 + (27/2)*n^2 - (21/2)*n.

Conjectures from Colin Barker, Jun 17 2018: (Start)

G.f.: 9*x*(1 + 5*x - 2*x^2) / (1 - x)^4.

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

(End)

EXAMPLE

Some solutions for n=4:

  1 1 1 1      1 0 0 1      1 1 0 0      1 0 1 0      1 0 0 1

  1 1 1 1      0 1 0 0      1 1 0 0      1 0 1 0      1 1 0 0

  1 1 0 1      0 1 0 0      0 1 0 0      1 0 1 0      1 1 0 0

  0 1 0 1      0 1 0 0      0 1 0 0      1 0 1 0      1 1 0 0

CROSSREFS

Cf. A207024.

Sequence in context: A063824 A207560 A207415 * A207364 A207786 A223189

Adjacent sequences:  A207017 A207018 A207019 * A207021 A207022 A207023

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 14 2012

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 September 26 22:11 EDT 2022. Contains 357051 sequences. (Running on oeis4.)