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One-Space Notchers
Keywords: Life & Death
One-space notchers are groups that consist of a chain on the second line, interrupted by a notch of one empty space on the second line and one stone on the third. The term was invented by James Davies. See also Notchers, Two-Space Notchers and Three-Space Notchers. The rule for one space notchers is: "Four die, Seven live". You may also remember this as: "Five and Six are unsettled".
Here's the proof that "Four die". Even if Black plays first, White always has an answer to keep his group dead. Black 1 is answered by White 2 and vice versa.
Here's proof that "Seven live". Even if White plays first, Black always has an answer to keep his group alive. The diagram shows one white attack that fails. You can verify for yourself that it doesn't matter where the notch is located. You can also verify that five- and six-space notchers are unsettled, i.e. that the black group is alive if Black plays first and dead if White plays first. If you don't know how to verify unsettled cases, look in the discussion of two space notchers.
Classification
Marked points: possible weaknesses ClassificationSee notchers for the coding.
Black lives with 1 122
dead
can live with 1
can live with 1
can live with 1
can live with 1 All 122 can live, except 122WW and 122WN which are dead 123
Black can make a ko
Black can make a ko
Black can live
Black can live (...)
Black can live. White can kill at 1. All 123 can live, except for 123WW, dead, and, 123WN and 123NW, where Black can make a ko. 133
Black can live at 1 or A.
Black lives. White 1 is the strongest move. Any other move is answered by Black 1.
Black lives. White 1 is the strongest move. Any other move is answered by Black 1. (...) 133WW makes ko. 133WN can make life. All other 133xx live TableSee notchers for the coding. 111WW D - 112WW D - 113WW D -- 114WW D -- 115WW D -- 116WW LD 122WW D -- 123WW D -- 124WW D -- 125WW LD 133WW KD - 134WW LD (Work in progress) Authors: BillSpight, DieterVerhofstadt This is a copy of the living page "One-Space Notchers" at Sensei's Library. ![]() |