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!)
A281051 Number of n X 3 0..1 arrays with no element equal to more than one of its horizontal and antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards. 1
0, 6, 68, 376, 1492, 4988, 15028, 42252, 113076, 291660, 731060, 1791052, 4306868, 10197068, 23828404, 55060556, 125999028, 285894732, 643864500, 1440442444, 3203438516, 7086237772, 15599703988, 34190878796, 74638727092, 162339448908 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

FORMULA

Empirical: a(n) = 5*a(n-1) - 6*a(n-2) - 4*a(n-3) + 8*a(n-4) for n>6.

Empirical g.f.: 2*x^2*(3 + x)*(1 + 2*x)*(1 + 4*x + 2*x^2) / ((1 + x)*(1 - 2*x)^3). - Colin Barker, Feb 15 2019

EXAMPLE

Some solutions for n=4:

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

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

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

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

CROSSREFS

Column 3 of A281056.

Sequence in context: A152390 A200059 A183470 * A006737 A128869 A186669

Adjacent sequences:  A281048 A281049 A281050 * A281052 A281053 A281054

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 13 2017

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 October 3 18:24 EDT 2022. Contains 357237 sequences. (Running on oeis4.)