Originally Posted by
desiresjab
5 and 17 are a strange pair. They are both 4n+1. Phi/4 is 16, so there are plenty of factors of two left. Yet when the diagonal divides them it partitions them to 9 and 7. Since they are mutually rejective with that many factors of two left, that is all the diagonal could do.
Sometimes the diagonal is forced to parttion an odd number into two odd ones, as in 7 and 11, when there are only two factors of two (the minimum), or break an even one into two odds of different value, such as for 5 and 11, where there are only three factors of 2. But this is the first time I have seen a highly even number partitioned unevenly. The diagonal always gets it right. I have not had time to check the "natural" pairs for for 5 and 17 yet to see what they say. There are only 16 of them, so it will not be difficult.