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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

Table of n, a(n) for n=1..32.

Giovanni Resta, Illustration of a(6)-a(30)

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

Adjacent sequences:  A261209 A261210 A261211 * A261213 A261214 A261215

KEYWORD

nonn

AUTHOR

V.J. Pohjola and Giovanni Resta, Aug 12 2015

STATUS

approved

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Last modified March 30 06:40 EDT 2020. Contains 333119 sequences. (Running on oeis4.)