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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 (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..11.

CROSSREFS

Cf. A000105, A001933, A234007, A234008, A234009, A234010.

Sequence in context: A076321 A000088 A071794 * A285002 A107378 A186998

Adjacent sequences:  A234003 A234004 A234005 * A234007 A234008 A234009

KEYWORD

nonn,more

AUTHOR

John Mason, Dec 18 2013

STATUS

approved

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Last modified October 18 12:52 EDT 2018. Contains 316321 sequences. (Running on oeis4.)