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!)
A261212 Maximum number of 1's in an fully symmetrical n X n binary matrix with no three 1's adjacent in a line along a row, column or diagonally. 1
1, 4, 4, 8, 16, 20, 25, 36, 41, 48, 64, 72, 81, 100, 109, 120, 144, 156, 173, 196, 213, 228, 256, 272, 300, 324, 349, 368, 401, 424, 457, 484 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Fully symmetrical refers to the four symmetry axes: horizontal, vertical and two diagonal.
Note that a(3k+2) = 4*(1+k)^2, for k=0,...,8, but a(29) = 401.
LINKS
FORMULA
a(n) <= A181018(n).
a(3k+2) >= 4*(k+1)^2.
EXAMPLE
For n=4, the matrix is
0 1 0
1 0 1
0 1 0
For n=6, the matrix is
1 1 0 0 1 1
1 0 1 1 0 1
0 1 0 0 1 0
0 1 0 0 1 0
1 0 1 1 0 1
1 1 0 0 1 1
CROSSREFS
Cf. A181018.
Sequence in context: A190100 A244421 A030168 * A112435 A232508 A028610
KEYWORD
nonn
AUTHOR
V.J. Pohjola and Giovanni Resta, Aug 12 2015
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 March 29 00:26 EDT 2024. Contains 371264 sequences. (Running on oeis4.)