For every integer n≥1, let P(n) denote the product of the first n odd numbers:
P(n)=1×3×5×⋯×(2n−1)
Prove that for all integers n≥1, P(n)=(2n)!/2^n×n!.
You can use Stirling's formula:
n! = sqrt(2*pi*n)*(n/e)^n