Is mathematics a part of natural sciences?

I’m applying to Penn CAS, and on the Common app there is a section where I have to enter a major of interest.
I’m interested in mathematics and natural sciences (I want to do computer science too, but unfortunately CAS doesn’t offer it…anyone know if I’m allowed to take CS from SEAS and take math from CAS?) but not so specifically decided to click “Mathematics” in the dropdown menu.
Is it valid to select “Undecided - natural sciences” if I’m mainly interested in maths? Is maths a part of natural sciences?

You said that you are interested in math and science. Now picture yourself you are actually in the math building, you go up one floor, it will take you from all math conjectures to cosmo galaxy in the entire physical universe. Physics dept is located right above math. When you think that you have studied enough all these mathematical structures long enough, you want to compute all their simulated quantum states, just walk out the math building, and you almost can count your footsteps across the street( careful for the street traffic) and you will go through a beautiful bioengineering entrance and the computer science dept and lab will be all yours. Hundreds and thousands of hacking enthusiasts have been through there every year from high schools and colleges. If you are curious more about other part of natural sciences, just turn around and back out the engineering quad, make a short short walk, material sciences and huge nanoscience lab is right in front of you. All the state-of-the-art facilities are all there for the nano world research. That is Penn’s unique science, math and technology complex. Pick your choice and be honest to yourself, go apply for your dream program. If you get in, take advantage of this no-other-place-to-be-found campus setting and have a lot of fun at PENN. Almost forgot your last question, and yes there are a lot of math, compsci and engineering shared classes, no restriction as long as they still have rooms. One warning though, compsci classes are always packed (that’s not too good news).

@soundfirst5 Thank you so much! I’ve never visited Penn, and now I really wish I had!