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!)
A230658 Number of nX3 0..2 black square subarrays x(i,j) with each element diagonally or antidiagonally next to at least one element with value 2-x(i,j) 1
0, 3, 15, 21, 135, 177, 1155, 1509, 9855, 12873, 84075, 109821, 717255, 936897, 6118995, 7992789, 52201935, 68187513, 445341435, 581716461, 3799265175, 4962698097, 32412020835, 42337417029, 276511126815, 361185960873 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 3 of A230661

LINKS

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

FORMULA

Empirical: a(n) = 9*a(n-2) -4*a(n-4).

Empirical: G.f. -3*x^2*(-1-5*x+2*x^2) / ( 1-9*x^2+4*x^4 ). - R. J. Mathar, Oct 27 2013

EXAMPLE

Some solutions for n=5

..x..0..x....x..2..x....x..1..x....x..0..x....x..2..x....x..2..x....x..2..x

..1..x..2....0..x..0....0..x..1....2..x..0....0..x..0....2..x..0....0..x..0

..x..1..x....x..0..x....x..2..x....x..2..x....x..2..x....x..0..x....x..1..x

..2..x..2....2..x..0....1..x..0....0..x..2....0..x..0....0..x..0....0..x..1

..x..0..x....x..2..x....x..1..x....x..0..x....x..2..x....x..2..x....x..2..x

CROSSREFS

Sequence in context: A076825 A259745 A118565 * A117801 A347303 A277585

Adjacent sequences:  A230655 A230656 A230657 * A230659 A230660 A230661

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 27 2013

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 28 03:58 EDT 2021. Contains 348313 sequences. (Running on oeis4.)