This article discusses what happens, and why, if you generate chains of sequences getting the next sequence from the differences between the adjacent terms in the sequence before it, eg (7, 2, 8, 3). . . .
This article explores the search for SP numbers, finding the few that exist and the proof that there are no more.
Investigate the sequences obtained by starting with any positive 2 digit number (10a+b) and repeatedly using the rule 10a+b maps to 10b-a to get the next number in the sequence.
Find all the periodic cycles and fixed points in this number sequence using any whole number as a starting point.