Compute the Fibonomial Coefficient
Python 67 bytes
f=lambda n,a=1,b=1:n&lt;1or a*f(n-1,b,a+b)
lambda n,k:f(n)/f(k)/f(n-k)

Call using a(n,k). Uses @Dennis fibonorial answer (is that allowed?), and a straightforward implementation of the question otherwise.