RECURSIVE SOLID
20 cubes survive
Divide a cube into 27 subcubes and remove the center plus the center cube of each face, leaving 20. Repeat on every survivor. Similarity dimension is log(20)/log(3) ≈ 2.72683.
FRACTAL TRIPEXPLORE INFINITYTAKE A TRIP ✦A recursive 3D sponge whose volume tends to zero while structure multiplies forever.

Divide a cube into 27 subcubes and remove the center plus the center cube of each face, leaving 20. Repeat on every survivor. Similarity dimension is log(20)/log(3) ≈ 2.72683.