Laxton introduced a group structure on the set of equivalence classes of linear recurrence sequences of degree 2. This result yields much information on the divisibilities of such sequences.

Equivalence-Based Instruction in Higher Education Publication Trend The graph below shows the total number of publications each year in Equivalence-Based Instruction in Higher Education.

The methods of cross-ratios, equivalence classes and metrics that were introduced in a previous paper (Altham 1970) are extended to three further problems. First the interdependence of the rows, ...