Plotting the excess values of sparse rulers in batches of maximal Wichmann rulers leads to a pattern called "Dark Satanic Mills on
a Cloudy Day" by N. J. A. Sloane. All the windows in the Dark
Mill are Wichmann constructions. Due to this pattern, it is believed Wichmann (1963)
solved the problem, with the caveats above.
Sloane, N. J. A. Sequence A326499 in "The On-Line Encyclopedia of Integer Sequences."Wichmann,
B. "A Note on Restricted Difference Bases." J. Lond. Math. Soc.38,
465-466, 1963.
