It's certainly made me, Mr Gregg, think. In 4G today we looked at the numbers Holly's dad had talked about, and used it for our counting circle:
These are all the "four times table plus one" numbers, they are the " 4 times something + 1" that Holly's dad talked to her about.
We looked for prime numbers among these. We used a 100 square, but it would have been better on a hundred-rectangle like this:
All the prime numbers are circled. The ones that we're looking at are the green ones. (It never works with the red primes.)
Then we found that all of them could be made by adding two square numbers.