Document here. Power Line analyzes it briefly, and finds that the denials that resulted in Flynn's guilty plea are actually pretty weak. Of the four things he supposedly lied about, two of them were more of a "I don't remember" than a lie, and the remaining two are still less than a firm denial. Given that Flynn was the incoming National Security Advisor and the conversations themselves were perfectly legitimate, I just don't see criminality here. Obviously a person will not remember his conversations with the perfect accuracy of a transcript. That's just how memory works.
If in fact Flynn did not accurately inform his superiors (Trump, Pence, etc) about the content of the conversation, that's a different question and possibly a firing offense regardless of intent. It's awkward, even potentially dangerous, to have your National Security Advisor talking to Russia and asking for things without passing that on. But that's a matter for Trump and Pence to consider, not something that criminal law really embraces. Especially not in a blatant perjury trap like this.
Actually, calling this a perjury trap seems inaccurate. A perjury trap is giving someone the opportunity to lie deliberately, knowing you can catch them in the lie. This was more like going to Flynn with the determination to manufacture a lie.