I recently noticed that, if you take the $(2n)$th row of Pascal's triangle, and alternately multiply and divide the numbers that crop up, almost everything cancels. For example, the 4th row (1 4 6 4 1) becomes $1/4 \times 6/4 \times 1$, which simplifies to $3/8$. I performed the same procedure for some later rows, and got $5/16$, $35/128$, $63/256$, $(3 \times 7 \times 11)/(2^{10})$, and $(3 \times 11 \times 13)/(2^{11})$.
All of the denominators seem to be powers of 2, which I don't know how to prove. Also, the fractions seem to me to be (very) slowly approaching 0, which I also don't know how to prove (if it's even true). Any assistance with either question would be greatly appreciated- I'm not very well versed in methods of proof.