Hull Moving Average Formula
Alan Hull uses three Weighted Moving Averages (WMA) in his formula:

Calculate the WMA for the Period (e.g. 13 Weeks).

Divide the Period by 2 and use the Integer value to calculate a second WMA.

Multiply the second WMA by 2 then subtract the first WMA.

Calculate the Square Root of the Period and take the Integer value.

Use the resulting Integer value to calculate a third WMA of the result from the first two WMAs.

Notation
Here is more mathematical notation for n periods:

WMA(Integer(SQRT(n)),WMA(2*Integer(n/2),data) - WMA(n,data))

Regards,

Fayez Azrak