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## 'Pinned Squares' printed from http://nrich.maths.org/

Pin those squares down! A geoboard is a piece of wood with pins
hammered into it. The diagram shows a 5 by 5 board with 25 pins set
out in a square array. Squares are made by stretching rubber bands
round specific pins as shown. What is the total number of squares
that can be made on a 5 by 5 board? How many squares can be made on
an N by N board?

A virtual pinboard is available

here.