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A217595 Number of free n-celled polyominoes without holes and odd side lengths. 1
1, 0, 1, 1, 2, 4, 7, 12, 35, 55 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

If you checkerboard color the vertices of the square lattice, a(n) is the number of orthogonal polygons of area n, which alternates between white and black vertices.

LINKS

Table of n, a(n) for n=1..10.

Giovanni Resta, Illustration of a(10) = 55.

EXAMPLE

For n=5 the a(5)=2 pentominoes are 'I' and 'X'.

CROSSREFS

Sequence in context: A190591 A027945 A079800 * A280028 A094271 A194422

Adjacent sequences:  A217592 A217593 A217594 * A217596 A217597 A217598

KEYWORD

nonn,hard,more

AUTHOR

Thomas Dybdahl Ahle, May 28 2013

EXTENSIONS

a(10) from Giovanni Resta, Jun 06 2013

STATUS

approved

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Last modified May 23 01:37 EDT 2019. Contains 323507 sequences. (Running on oeis4.)