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

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A185552 1/3 the number of n X 2 0..2 arrays with every element equal to exactly one or two of its horizontal and vertical neighbors. 1
1, 5, 26, 120, 576, 2768, 13256, 63544, 304608, 1460072, 6998680, 33547360, 160805064, 770799288, 3694731616, 17710240936, 84891859544, 406918677600, 1950514582792, 9349551515000, 44815924117856, 214819614744552 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 2 of A185559.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..200

FORMULA

Empirical: a(n) = 3*a(n-1) + 7*a(n-2) + 8*a(n-3) - 8*a(n-5).

Empirical g.f.: x*(1 - x)*(1 + 3*x + 7*x^2 + 6*x^3) / (1 - 3*x - 7*x^2 - 8*x^3 + 8*x^5). - Colin Barker, Apr 16 2018

EXAMPLE

Some solutions for 4 X 2 with a(1,1)=0!

..0..0....0..2....0..2....0..0....0..0....0..0....0..0....0..0....0..0....0..0

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

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

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

CROSSREFS

Cf. A185559.

Sequence in context: A293799 A211606 A005499 * A171702 A254825 A272123

Adjacent sequences:  A185549 A185550 A185551 * A185553 A185554 A185555

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 31 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 December 4 13:06 EST 2021. Contains 349526 sequences. (Running on oeis4.)