The order 
L-polyomino consists of a vertical line of 
squares with a single additional
square attached at the bottom.
L-Polyomino
See also
Gnomon, Skew Polyomino, Square, Square Polyomino, Straight PolyominoExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "L-Polyomino." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/L-Polyomino.html