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Generalized forcing chain

The following position advancedcolouring.sdk was given by nick70.

One easily obtains

Use the forcing chain on the yellow squares 53-32-28-83-35, that is, in coordinates, (5,3)3 > (6,2)2 > (5,1)8 > (5,6)3 > (5,3)5. It follows that position (5,3) is 5.

In row 6, there is a 1,5,7 subset in columns 3,8,9, so nothing else is in these three positions.

Use the generalized forcing chain (6,2)2 > (5,1)8 > (5,6)3 >> (5,9)4 >>> (5,7)2 > (4,8)7 > (6,8)5 > (6,9)1 > (6,3)7 > (8,3)3 > (8,2)2 > (6,2)3. (Here >, >>, >>> mean that the following claim follows from the previous one, two, or three claims.) It follows that position (6,2) is 3.

The rest is straightforward.

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