Pseudo-polyomino

A pseudo-polyomino, also called a polyking, polyplet or hinged polyomino, is a plane geometric figure formed by joining one or more equal squares edge-to-edge or corner-to-corner at 90°.

The name "polyking" refers to the king in chess.

The n-kings are the n-square shapes which could be occupied by a king on an infinite chessboard in the course of legal moves.

Golomb uses the term pseudo-polyomino referring to kingwise-connected sets of squares.

[1] There are three common ways of distinguishing polyominoes and polykings for enumeration:[1] The following table shows the numbers of polykings of various types with n cells.