login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A234009 Free polyominoes with 4n squares, having 90-degree rotational symmetry about a square corner. 5
1, 1, 4, 10, 35, 114, 403, 1432, 5239, 19271, 71820, 269417, 1017920, 3864879 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
The number of free polyominoes of size 4n that have 90-degree rotational symmetry about a point that coincides with the corner of a square, independently of any other symmetries. Note that for polyominoes which have a hole in the center, the center of rotation will be the corner of a square within the hole, rather than being the corner of a square of the polyomino itself. The sequence is defined for 4n rather than n as polyominoes of size not multiple of 4 cannot have the required symmetry.
LINKS
CROSSREFS
Sequence in context: A030003 A339845 A363465 * A198324 A149175 A149176
KEYWORD
nonn,hard,more
AUTHOR
John Mason, Dec 18 2013
EXTENSIONS
a(8)-a(14) from John Mason, Dec 13 2021
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 19 03:27 EDT 2024. Contains 370952 sequences. (Running on oeis4.)