What is the mathematical notation for a Pulse Generator + If blocks in Simulink?

Hi,

I have a value of I1 and I2. I want the value of I1, except for one time every 28 days/seconds (does not matter). I modelled this in Simulink with I1=4, I2=1:

Now I have my desired model, I need to correctly note in mathematical notation for a report. How would I do this? Something like a Fourier series, or an if statement, or something else?

[DB]

I thought of something like:

I = {I2, every 28 days
    {I1, else

But it's not 100% correct I think. Can anybody help?