Ttetromino
Ttetromino  
Pattern type  Miscellaneous  

Number of cells  4  
Bounding box  3×2  
Discovered by  John Conway  
Year of discovery  1970  

Ttetromino is one of 5 tetrominoes. It is a common predecessor of the traffic light, and when paired with another Ttetromino it can become a predecessor of the pulsar.
In a cylindrical grid with a width of 6, the Ttetromino is always a replicator. It copies itself on the 15th and 40th generations of every 40 generations. However, because it leaves behind blocks, blinkers, and sparks, it does cleanly replicate itself until after 200 generations. It acts much the same way as the replicator in Highlife because the two copies of the Ttetromino appear offset in opposite directions of the original. Also, two replicators will destroy each other if they are next to each other. The Ttetromino replicates orthogonally and 35 cells away from the original.
In other rules
The Ttetromino exhibits interesting behaviour in other lifelike cellular automata. It is a c/4 orthogonal spaceship in 32 totalistic rules, B345/S126 to B345678/S12678, with the tip of the T being the trailing edge; it is also a c/4 orthonal spaceship in various nontotalistic rules, e.g. GlideLife, though it evolves differently.
In the nontotalistic automaton tlife, the Ttetromino is an extremely common c/5 orthogonal spaceship, with the tip of the T being the leading edge.
In the rule B34tw5y/S23, it acts almost like a twodimensional replicator, however the copies react with each other to form 4 17c/47 orthogonal glider rakes. A similar reaction happens in wlife (B34w/S23), forming 4 2c/5 orthogonal beehive puffers.
See also
External links
 Ttetromino at the Life Lexicon
 Ttetromino (rule b3s2i34q) at Adam P. Goucher's Catagolue
 Ttetromino (rule b345s126) at Adam P. Goucher's Catagolue
 Glider 26 at David Eppstein's Glider Database