OFFSET
2,1
COMMENTS
For even n > 2 the only symmetry possible is rotation by 180 degrees. For odd n > 1 the only symmetries are reflections either horizontally or vertically. - Andrew Howroyd, Apr 15 2016
EXAMPLE
From Andrew Howroyd, Apr 15 2016: (Start)
Case n=4: There are 2 nonisomorphic symmetrical solutions (see illustration below). a(4)=(A068381(4)/8 + 2)/2 = 7.
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| __ __| | __ | |
| | | | | | | | | |
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|__.__.__.__| |__|__.__.__|
Case n=5: There are 7 nonisomorphic symmetrical solutions (see illustration below). a(5)=(A068381(5)/8 + 7)/2 = 44.
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| |__ __| | | | __ | | | __| |__ | | | | | | |
| __| |__ | | | | | | | | | __ | | | | | | | |
| |__.__.__| | | |__| |__| | | |__| |__| | | |__| |__| |
|__.__.__.__.__| |__.__.__.__.__| |__.__.__.__.__| |__.__.__.__.__|
__.__.__.__.__. __.__.__.__.__. __.__.__.__.__.
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| __| |__ | | | | | | | |__| | | |__|
| | __ | | | | | | | | | __| |__ |
| |__| |__| | | |__| |__| | | |__.__.__| |
|__.__.__.__.__| |__.__.__.__.__| |__.__.__.__.__|
(End)
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 03 2002
EXTENSIONS
a(7)-a(15) from Andrew Howroyd, Apr 15 2016
STATUS
approved