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1. Center bar:

Middle row, cols 2-4 = positions (3,2)-(3,3)-(3,4)

This can be rotated to vertical or reflected, but always stays at the center.

 

2. Off-center:

Top row, cols 1-3: (1,1)-(1,2)-(1,3)

Top row, cols 2-4: (1,2)-(1,3)-(1,4)

Top row, cols 3-5: (1,3)-(1,4)-(1,5)

But these are all equally distant from their accompanying edge; by symmetry, place (1,1)-(1,2)-(1,3) is same as (1,3)-(1,4)-(1,5) under reflection.

So for each "run of 3" not at the center, there are only two types by distance from the edge: edge and one-step-in.

So per orientation, horizontal and vertical, that gives:

Center

Edge

One in from edge

But rotations mix horizontals and verticals. So these three types exhaust the possibility for straight bars:

Case 1: Centered three-in-a-row (middle row & col)

Case 2: Edge three-in-a-row (either on top/left or bottom/right edge)

Case 3: Offset three-in-a-row (one away from edge, but not center)

Centered bar: ((3,2)-(3,3)-(3,4)) (also ((2,3)-(3,3)-(4,3)), rotated)

Edge bar: ((1,1)-(1,2)-(1,3)) (can be rotated/reflected to any edge)

Offset bar: ((1,2)-(1,3)-(1,4))

So 3 distinct orbits for straight bars.

 

B. Diagonal Bars:

Now, consider the diagonal three-in-a-row:

((1,1)-(2,2)-(3,3))

((2,2)-(3,3)-(4,4))

((3,3)-(4,4)-(5,5))

Similar situation on other main diagonal.

Only possibilities for "bar on a diagonal":

Main diagonal, centered

Central run: ((2,2)-(3,3)-(4,4))

Main diagonal, edge

Edge run: ((1,1)-(2,2)-(3,3))

((3,3)-(4,4)-(5,5))

The two runs at the ends of the diagonal are symmetric by 180° rotation.

Similarly, diagonals above/below the main diagonal, but only have length 3.

Also, shorter diagonals: length 3, only one way to pick three in a row.

But are these different up to symmetry? For a 5x5, all "sloping" bars at the edge are the same under symmetry.

Diagonal (main): Centered and edge.

 

And diagonal bars not on the true main diagonal or true anti-diagonal can be rotated to each other.

So, just as before:

Diagonal centered

Diagonal edge

So, in total, for "three-in-a-row" on a diagonal, we only get two types: centered and edge.

 

In conclusion, there are 5 distinct types of three-in-a-row colorings (orbits under symmetry):

Final Answer;

\(\boxed{5}\)

There are 5 distinct colorings of three squares in a row (of any direction) in a 5 by 5 grid, up to rotation and reflection.

vor 3 Stunden