Some solutions to Langford's Problem fit a pattern and can be constructed.
This is one such pattern found by Roy O. Davies
In the Geogebra screen, use the sliders to specify N. The app will compute 4N and show the construction.
Mark and unMark the checkbox labeled "Subtract 1", and note that very little changes.
Note that there are four "patterns", each involving N-1 elements.

In the Geogebra screen, use the sliders to specify N. The app will compute 4N and show the construction.
Mark and unMark the checkbox labeled "Subtract 1", and note that very little changes.
Note that there are four "patterns", each involving N-1 elements.