# Calculating Bayes Factor from Z score, n, and No

I'm completely stuck on how to get this answer from a course below.

I guessed the answer, but I'm lost on how they get to it. I did the following in R

N_0 = 1
n = 1000
z = 2.055
BF = (((n+N_0)/n)^0.5)* exp((-1/2)*(n/(n+N_0)*z^2))
BF
[1] 0.121371


Given the Bayes Factor is 3.83, I know I've screwed up somewhere (and got the right answer by accident.

Can anyone help spot my error?