How to evaluate modified bessel functions of even integer order and with negative argument

Question

I am trying to compute modified Bessel functions of nonnegative even integer orders but with negative argument in R. However, I am drawing a blank, because the function as coded in R says it only holds for nonnegative arguments. My arguments are real, say $\mathbb{I}_{2j}(-0.24)$ and I wonder if there is a formula to get them from other values.

Answer 1

As mentioned by A rural reader, the solution is indeed in dlmf.nist.gov/10.74 and uses the fact that $\mathbb{I}_{2n}$ is even.