1 polyominos of size 1
*

1 polyominos of size 2
*
*

2 polyominos of size 3
*   
* * 
* **

1 polyominos of size 4
* 
**
* 

1 polyominos of size 5
 * 
***
 * 

0 polyominos of size 6
Total 2-indecomposible polyominos = 6
Size >= 2 2-indecomposible polyominos = 5
Size >= 4 2-indecomposible polyominos = 2