Tillson T1 to T4

This is to expand on a previous publication on Tillson's T3 and add a T4 signal.

For the filter f = (1+a)x-ax^2
T1 = f
T2 = f*f
T3 = f*f*f
T4 = f*f*f*f
The above plotted produces a ribbon set of moving averages.