# Wichmann-like Rulers

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A sparse ruler is a rod of integer length with a minimal number of marks so that all distances 1 to can be measured. With 1 to 9, its five marks are at with differences between marks . The differences 1 to 9 are , , , , , , , , .

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Contributed by: Ed Pegg Jr (August 2019)

Open content licensed under CC BY-NC-SA

## Details

References

[1] B. Wichmann, "A Note on Restricted Difference Bases," *Journal of the London Mathematical Society*, s1-38(1), 1963 pp. 465–466. doi:10.1112/jlms/s1-38.1.465.

[2] A. D. Robison. "Parallel Computation of Sparse Rulers." (Aug 7, 2019) software.intel.com/en-us/articles/parallel-computation-of-sparse-rulers.

[3] P. Luschny. "Perfect and Optimal Rulers." (Aug 7, 2019) oeis.org/wiki/User:Peter_Luschny/PerfectRulers.

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