Константин: Why with P16-R19-S19-N19O19 is seki? White has one more liberty at T19, and black can't T19 first because of self-atari. So white can Q19 or R18.... And it's not a seki, there are two eyes
Sadaharu: The variation you mentioned is already inside
caranthir: To nate2: the sequence you mentioned shows a suboptimal response from the opponent, and in that case we should indeed live with points and not have seki.
nate2: With the sequence P16, R19, S19, N19, the only accepted last move is R18, but O19 is Seki. Obviously Seki is a worse result, but the instructions say that Seki is a success. Maybe at the top it should say No Seki next to No Ko
Ivan Detkov: Seki is a success indeed. I do not see a variant allowing to live without seki with the best play from both sides. Do you?
posivb: 1)
C19G19F19B19A19 is wrong. It's a ko. The problem is "White to live. (No Ko)"
2)
E16B19C19G19F19 seems to work too.
Farkas: I disagree with your comment. Actually A19 is a hanami ko, which force the opponent to waste a ko-threat. Even after your opponent take it back, you can still connect and live.
tsumego doesn t upload...