Many times scientistics and pseudo-scientists want proof that there is a God. It is my opinion that if someone is skeptical about the existence of God, then they will also be skeptical about any 'proof' that you might provide. Typically, anything religious (the Bible in particular) will be rejected as proof because it is deemed biased. In Romans, Paul tells us to look at creation, you can find God there.
Roman 1:20
For since the creation of the world God's invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that men are without excuse.
A year or so ago, I was reading some articles in Wikipedia (everybody does that right?) and stumbled on an article about a mathematical equation that, should make any skeptic take pause. This equation is referred to as Euler's Identity after the famous mathematician Leonhard Euler.
Here's the equation:

This equation relates the 5 most important mathematical constants into one simple beautiful relationship.
e is the base of natural logarithm's (also called Euler's number). It is a non-terminating, non-repeating decimal number 2.71828 18284 59045 23536...
i is an imaginary number defined as the square root of -1.
pi (the greek symbol in the equation) is the ratio of the circumference of a circle to its diameter. It is another non-terminating, non-repeating decimal 3.14159 26535 89793 23846...
This relationship amazes me because of the complexity of the numbers involved and the simplicity and beauty of the relationship. It is really beyond my knowledge and ability to explain much about this equation or its significance, you can find more information about it here.
God is speaking all around us, even in mathematics. All we have to do is listen.