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1/4 of the number of islands of ones fitting in an n X n array symmetric about the diagonal and under 90-degree rotation with all ones connected only either two adjacent vertically or two adjacent horizontally.
0

%I #5 Nov 25 2018 12:22:59

%S 0,0,0,1,1,1,3,3,4,6,6,7,10,10,12,15,15,17,21,21,24,28,28,31,36,36,40,

%T 45,46,50

%N 1/4 of the number of islands of ones fitting in an n X n array symmetric about the diagonal and under 90-degree rotation with all ones connected only either two adjacent vertically or two adjacent horizontally.

%e 8 X 8 example with 12 islands:

%e 0 0 1 0 0 1 0 0

%e 0 0 1 0 0 1 0 0

%e 1 1 0 1 1 0 1 1

%e 0 0 1 0 0 1 0 0

%e 0 0 1 0 0 1 0 0

%e 1 1 0 1 1 0 1 1

%e 0 0 1 0 0 1 0 0

%e 0 0 1 0 0 1 0 0

%K nonn

%O 1,7

%A _R. H. Hardin_, Oct 19 2008