[seqfan] A sequence from the T-square fractal

[Jaume Oliver i Lafont]

If we count all the squares, not only those at the border, the
solution is 4,28,148,700,3124,13468,56788,235900,969844,
which is 4*A005061=4*(4^n-3^n)

At each step, the area of the previous square is multiplied by four
and three squares (an "L") are added at each available corner.

Jaume