Problem 161

Triominoes

A triomino is a shape consisting of three squares joined via the edges. There are two basic forms:

If all possible orientations are taken into account there are six:

Any n by m grid for which nxm is divisible by 3 can be tiled with triominoes.

If we consider tilings that can be obtained by reflection or rotation
from another tiling as different there are 41 ways a 2 by 9 grid can be
tiled with triominoes:

In how many ways can a 9 by 12 grid be tiled in this way by triominoes?

**
These problems are part of
Project Euler
and are licensed under
CC BY-NC-SA 2.0 UK
**