For n = 2, the a(2) = 5 solutions are:
+---+ +---+---+ +---+---+ +---+---+ +---+---+
| | | | | | | | | | | | | |
| * | | **|** | | * | * | | **|** | | **|** |
| * | | | * | | * | * | | * | | | * | * |
+---+ +---+---+ +---+---+ +---+---+ +---+---+
| * | | | * | | * | * | | * | | | * | * |
| * | | **|** | | **|** | | **|** | | * | * |
| | | | | | | | | | | | | |
+---+ +---+---+ +---+---+ +---+---+ +---+---+
|