SAP IBP - calculation crossing time period (recursive KF3(t+1)=KF3(t) x Factor + KF1)

Hi, I am struggling

I have the following scenario

KF2(0)= 0

KF2(t+1)=KF3(t) x Factor

KF3(t+1)=KF2(t+1) x Factor + KF1

in a table (with factor = 70% and t represent a time bucket)

t || 0 || 1 ||2 || 3

KF1 || 23 || 34 || 40 || 40

KF2 || 0 || 16.1 || 35.1 || 52.5

KF3 || 23 || 50.1 || 75.1 || 92.5

How to calculate KF3 ?

Many thanks in advance,

BR,

Jean-Luc Hospital