This problem has me completely stumped. Fortunately I needn't feel bad about it because I'm not nearly strong enough to be supposed to solve it.
This is the best I can do. If for some reason black responds to at , then white can live with the sequence -. After , white threatens to capture the corner, and if black defends it by capturing for example, then white a makes life at b or c. Black will of course not answer at , but maybe there is some aji with the marked stones to make black answer at .
Maybe this is the answer. After , black has a problem. White can play at a to get an eye at b (or capture black), or at c to capture either black or black .
After white threatens a capture on the left and a ladder on the right.
Does anyone see a refutation? (maybe at a?)
Seems to work for white.
Seems like a solved problem to me.
Black can answer with the atari. This problem doesn't seem solved to me. There is no ko after 10. -- Sampi
What about not exchanging 5 for 6? If black at a, white captures, and the diagram reverts to "If for some reason black responds to at " at top.
--Stickleback (now 1k)