d4rkm4tter: I looked into the history. The initial position got changed and then the problem didn't make sense anymore. Here is the original position with one less stone on the outside which makes the opponent block instead of throw in.
posetcay: As pointed out by the previous comment, this tsumego has no solution. I do not see any way to fix it, so I recommend just deleting this tsumego.
Thorstein Thorsteinsson: After B5-A3-B4 white can throw in at F1 I don't see how black continues after that. And even after white J4 - black F1 white can play the key point at B1 and again wins? Unless I missed something this problem doesn't have a solution.
posetcay: Yes, it is not possible to kill after F1.
Added B19 as an alternative to A18.