No dead ends near the entrance, 21,477,560 21,485,005
Try it online!
Yay, 21 million. The giant horizontal segments up to row 19 are also removed, so about 20% of the entire grid is just an open space....
C++ and the library from lingeling
Summary: A new approach, no new solutions, a nice program to play
with, and some interesting results of local non-improvability of the
known solutions. Oh, and some ...