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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A210996 Number of free polyominoes with 2n cells. 5
1, 1, 5, 35, 369, 4655, 63600, 901971, 13079255, 192622052, 2870671950, 43191857688, 654999700403, 9999088822075, 153511100594603, 2368347037571252, 36695016991712879, 570694242129491412, 8905339105809603405 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

It appears that we can write A216492(n) < A216583(n) < A056785(n) < A056786(n) < a(n) < A210988(n) < A210986(n), if n >= 3. - Omar E. Pol, Sep 16 2012

LINKS

Table of n, a(n) for n=0..18.

Herman Tulleken, Polyominoes 2.2: How they fit together, (2019).

Eric Weisstein's World of Mathematics, Polyomino

Wikipedia, All 5 free tetrominoes, Illustration of a(2) = 5.

Wikipedia, All 35 free hexominoes, Illustration of a(3) = 35.

Wikipedia, All 369 free octominoes, Illustration of a(4) = 369.

Wikipedia, Polyomino

EXAMPLE

For n = 1 there is only one free domino. For n = 2 there are 5 free tetrominoes. For n = 3 there are 35 free hexominoes. For n = 4 there are 369 free octominoes (see link section).

CROSSREFS

Bisection of A000105.

Cf. A000988, A056785, A056786, A210988, A210997, A216492, A216583.

Sequence in context: A233860 A258902 A125864 * A204290 A059865 A247596

Adjacent sequences:  A210993 A210994 A210995 * A210997 A210998 A210999

KEYWORD

nonn

AUTHOR

Omar E. Pol, Sep 15 2012

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 November 12 22:04 EST 2019. Contains 329079 sequences. (Running on oeis4.)