Given I'm spending 3-4 days a week with 5th & 6th graders, teaching them Python, I'm looking for ways to sync with what Common Core says they should be learning math-wise.
They general strategy here is to look for topics already in the curriculum and develop coding skills around those topics.
Turns out that prime versus composite is important at that age, and the classic algorithm used to teach that is the Sieve of Eratosthenes. Most coders have written at least one of those.
Since we're transitioning from block-based MIT Scratch with not much keyboarding, to full-fledged lexical Python, I'm thinking to assess facility with keyboarding (typing) by having them hand-enter a Sieve, and running it to check for any syntax errors.
While we're still doing natural and whole numbers it makes sense to look at other number series as well, ones we can explore using very simple Python.
Triangular and square numbers, then polyhedral number sequences, such as successive shells around a nucleus. 1, 12, 42, 92...
Pascal's Triangle is an important hub for studying number sequences. It even embeds the Fibonacci Numbers.