Well explained by Tom, from Cottenham Village College

The answer I got for Tn is: 8Tn+1=(2n+1)2


The 2n+1 part is because the diagram looks like this for T3

square arrangement
2Tn form a rectangle n by n+1

The four rectangles rotate around the centre and together make a square of side n+(n+1)

So we get the equation 8Tn+1=(2n+1)2