A145806 - OEIS

A145806

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

%I #5 Nov 25 2018 12:29:03

%S 0,0,0,1,1,2,3,3,4,6,6,8,10,11,12,15,16,18,21,23,25

%N 1/4 of the number of islands of ones fitting in an n X n array symmetric 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 0 1 0 0 1 0

%e 1 1 0 1 0 0 1 0

%e 0 0 1 0 1 1 0 0

%e 0 0 1 0 0 0 1 1

%e 1 1 0 0 0 1 0 0

%e 0 0 1 1 0 1 0 0

%e 0 1 0 0 1 0 1 1

%e 0 1 0 0 1 0 0 0

%K nonn

%O 1,6

%A _R. H. Hardin_, Oct 19 2008