OFFSET
1,2
COMMENTS
The sequence considers reflections and rotations as distinct tilings.
The polyominoes being tiled and the tiles themselves may be with or without holes.
The number of tilings of a 2-by-n rectangle is 2*A005668(n). Along with the fact that a(n+1) >= 2*a(n), because any added cell can either remain a monomino, or be joined to a neighboring polyomino, this yields a(1) through a(8). Other shapes take over beginning at a(9). - Charlie Neder, Sep 10 2025
EXAMPLE
a(3) = 4 because any tromino can be tiled by (1) a tromino, (2) 3 monominoes, and (3) a monomino and a domino in two distinct ways.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
John Mason from an idea of Craig Knecht, Nov 07 2023
STATUS
approved
