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
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
KEYWORD
nonn
AUTHOR
V.J. Pohjola and Giovanni Resta, Aug 12 2015
STATUS
approved