A145817 Number of islands of ones fitting in an n X n array symmetric under 180 degree rotation with all ones connected only either three adjacent vertically or three adjacent horizontally.

0, 0, 2, 2, 4, 6, 8, 10, 14, 14, 19, 24, 26, 30, 38

Offset

1,3

Links

Table of n, a(n) for n=1..15.

Example

8 X 8 example with 10 islands
.1.0.1.1.1.0.0.0
.1.0.0.0.0.1.1.1
.1.0.1.1.1.0.0.0
.0.0.0.0.0.1.1.1
.1.1.1.0.0.0.0.0
.0.0.0.1.1.1.0.1
.1.1.1.0.0.0.0.1
.0.0.0.1.1.1.0.1

Crossrefs

Sequence in context: A202102 A300576 A118303 * A145809 A309711 A116859

Adjacent sequences: A145814 A145815 A145816 * A145818 A145819 A145820

Keyword

nonn

Author

R. H. Hardin, Oct 20 2008

Status

approved