Jasper32 wrote:Still nobody has replied to a previous post where I asked if the forcing chain of:

r8c7=5 >r8c9=7>r4c9=2>r6c8=5>r5c7<>5

is valid. I am curious if I did that correctly.

There are many more knowledgeable about chains than myself, but I'm sure that it isn't a proper chain. Your initial assertion of r8c7=5 would result in r5c7<>5 if it were true. All you've done is find a chain that agrees with the initial assertion. A chain needs to do more than that -- unless it's a continuous Nice Loop.

Since r8c7=7 is actually true, your initial assertion turns out to be false, but your elimination turns out to be true. That qualifies as Lucky.