Block on cover

	Block on cover
	<a href="/wiki/File:Blockandtwotails.png" class="image" title="Block on cover image"><img alt="Block on cover image" src="/w/images/4/4d/Blockandtwotails.png" decoding="async" width="113" height="113" /></a>
	<a href="/wiki/File:Blockandtwotails.png" class="image" title="Block on cover image"><img alt="Block on cover image" src="/w/images/4/4d/Blockandtwotails.png" decoding="async" width="113" height="113" /></a>
	View static image
Pattern type	Strict still life
Number of cells	12
Bounding box	5×5
Frequency class	19.9
Discovered by	Unknown
Year of discovery	Unknown
Rules
Outer-totalistic rules	B/S23 – B3678/S012345678
Important rules	Conway Life, HighLife
# of rules	211 = 2048
Isotropic rules	B/S2aek3ar – B2ikn34-ai5-kr678/S012345678
Glider synthesis
Fewest gliders	4
Catagolue-generated RLE	blockandtwotails_synth.rle
Uploaded synthesis RLE	blockandtwotails_synth.rle
Pattern files
Plaintext	blockandtwotails.cells
RLE	blockandtwotails.rle
Identifiers
apgcode	xs12_178br
Niemiec ID	12.111
Pentadecathlon ID	12.3

Block on cover is a 12-bit still life. It consists of a block stabilizing a cover.

Commonness

Block and two tails is the fifty-sixth most common still life in Achim Flammenkamp's census, being less common than trans-hook and R-bee but more common than cis-boat on dock.^[1] It is also the sixty-nineth most common object on Adam P. Goucher's Catagolue.^[2]

On April 4, 2007 Dean Hickerson found a 4-glider synthesis of this still life.^[3]

↑ Achim Flammenkamp (September 7, 2004). "Most seen natural occurring ash objects in Game of Life". Retrieved on January 15, 2009.
↑ Adam P. Goucher. "Statistics". Catagolue. Retrieved on June 24, 2016.
↑ Dean Hickerson's 2, 3, and 4-glider syntheses pattern collection