Update docs/src/implementations.md

Co-authored-by: Seth Axen <seth@sethaxen.com>

docs/src/implementations.md

@@ -38,4 +38,4 @@ To define a new FFT implementation in your own module, you should
  * `AbstractFFTs.RealInverseProjectionStyle(d::Int)`, for plans which expect an input with a halved dimension analogously to [`irfft`](@ref), where `d` is the original length of the dimension.
 
 The normalization convention for your FFT should be that it computes yₖ = ∑ⱼ xⱼ exp(-2πi jk/n) for a transform of
-length n, and the "backwards" (unnormalized inverse) transform computes the same thing but with exp(+2πi jk/n).
+length ``n``, and the "backwards" (unnormalized inverse) transform computes the same thing but with ``\exp(+2\pi i jk/n)``.