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Impuzzable
This is about a fiendishly difficult jigsaw and how to solve it
using a computer program.
Make your own double-sided magic square. But can you complete both sides once you've made the pieces?
The puzzle can be solved with the help of small clue-numbers which are either placed on the border lines between selected pairs of neighbouring squares of the grid or placed after slash marks on the intersections between two diagonally adjacent squares.
An introduction to the binomial coefficient, and exploration of some of the formulae it satisfies.
This article for teachers suggests activities based on pegboards, from pattern generation to finding all possible triangles, for example.