Help Identifying Filter & Governing Equations

I'm currently trying to make a few line traps and have been doing a little reading. I found that these guys used a T filter with some lumped element components. They didn't describe how they did it so I'm a little confused.

I am trying to block a range of frequencies. They blocked 1 MHz to 10 MHz (they get high attenuation in this band). I want to block 4.5 MHz to 21 MHz and also block 30 kHz to 100 kHz (components might get big but don't care).

I want to pass 50/60 Hz and have input/output impedance of filter to be 50 Ohms (as close as possible).

Attached is a picture of the T-filter. Can someone help me understand what the governing equations are so I can get the values that will give me high attenuation in the above bands. Thanks. The previous guys achieve 60 attenuation in the 1-10 MHz scenario (for reference).

Should I just find the transfer function but the impedance looks tricky.

Any takers?