(In reply to Generalised approach
Excellent finding, Harry!
I thought that your main points got buried, so I am reposting them. (No original work on my part was done)
You astutely wrote:
So for a24 to be an integer, (a2 – a1) must be divisible by 222
If only positive integers are allowed for (a1, a2) then choose (1, 222 + 1).
If zero is allowed then (0, 222) is best, as Jer recommended.
If all integers are allowed then (-221, 221) have the smallest abs. values