login
This site is supported by donations to The OEIS Foundation.

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A234006 Free polyominoes with 2n squares, having reflectional symmetry on axis that coincides with edges. 5
1, 2, 4, 11, 35, 114, 392, 1381, 4998, 18292, 67791, 253182, 952527, 3603389, 13699516, 52300071, 200406183, 770424072, 2970400815, 11482442855, 44491876993, 172766491178, 672186631950, 2619995178793, 10228902801505, 39996341268584, 156612023001490, 614044347934591 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The number of free polyominoes of size 2n that have reflectional symmetry on a horizontal or vertical axis that coincides with the edges of some of the squares. The sequence is defined for 2n rather than n as odd-sized polyominoes cannot have the required symmetry.

LINKS

Table of n, a(n) for n=1..28.

FORMULA

a(2*n+1) = A151525(2*n+1), a(2*n) = A151525(2*n) + A182645(n) - A001168(n). - Andrew Howroyd, Dec 05 2018

CROSSREFS

Cf. A000105, A001168, A001933, A151525, A182645, A234007, A234008, A234009, A234010.

Sequence in context: A076321 A000088 A071794 * A285002 A107378 A186998

Adjacent sequences:  A234003 A234004 A234005 * A234007 A234008 A234009

KEYWORD

nonn

AUTHOR

John Mason, Dec 18 2013

EXTENSIONS

a(12)-a(28) from Andrew Howroyd, Dec 05 2018

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 17 06:41 EST 2019. Contains 319207 sequences. (Running on oeis4.)