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

 

Logo

Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 5000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A245620 Number of unitary polyominoes with n cells.  A unitary polyomino is a polyomino whose edges all have length 1. 1
1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 2, 2, 3, 4, 7, 10, 17, 28, 47, 69 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,11

COMMENTS

If a unitary polyomino is colored in checks, all cells on each boundary have the same color.  This characterizes unitary polyominoes.

LINKS

Table of n, a(n) for n=1..20.

Alberto Del Lungo, Massimo Mirolli, Renzo Pinzani, and Simone Rinaldi, "A Bijection for Directed Polyominoes," Discrete Mathematics and Theoretical Computer Science Proceedings, AA (2001), 133-144 (PDF

George Sicherman, Catalogue of Unitary Polyominoes

EXAMPLE

The monomino (a single square) is unitary.  The domino, trominoes, and tetrominoes are not.  The X pentomino is unitary; the other pentominoes are not.

CROSSREFS

Cf. A000105, number of free polyominoes with n cells.

Cf. A245660, unitary polyominoes without holes.

Sequence in context: A003179 A153934 A143590 * A059348 A110871 A243856

Adjacent sequences:  A245617 A245618 A245619 * A245621 A245622 A245623

KEYWORD

nonn,hard,more,nice

AUTHOR

George Sicherman, Jul 27 2014

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified December 10 00:24 EST 2016. Contains 278993 sequences.