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!)
A227265 Number of n X 2 0,1 arrays indicating 2 X 2 subblocks of some larger (n+1) X 3 binary array having a sum of three or less, with rows and columns of the latter in lexicographically nondecreasing order. 1
3, 8, 16, 30, 54, 93, 153, 241, 365, 534, 758, 1048, 1416, 1875, 2439, 3123, 3943, 4916, 6060, 7394, 8938, 10713, 12741, 15045, 17649, 20578, 23858, 27516, 31580, 36079, 41043, 46503, 52491, 59040, 66184, 73958, 82398, 91541, 101425, 112089, 123573 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = (1/24)*n^4 + (1/12)*n^3 - (1/24)*n^2 + (47/12)*n - 1.

Conjectures from Colin Barker, Sep 07 2018: (Start)

G.f.: x*(3 - 7*x + 6*x^2 - x^4) / (1 - x)^5.

a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>5.

(End)

EXAMPLE

Some solutions for n=4:

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

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

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

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

CROSSREFS

Column 2 of A227269.

Sequence in context: A000233 A002624 A293358 * A295960 A068039 A188123

Adjacent sequences:  A227262 A227263 A227264 * A227266 A227267 A227268

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jul 04 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 11 00:55 EDT 2022. Contains 356046 sequences. (Running on oeis4.)