I certainly used Lisp notation, but if you think it's "just Lisp" then you're kind of missing the point. It's not just "just Lisp", it's "just lambda". There is nothing else in there, no primitives, no numbers, no CAR, CDR, CONS, COND or QUOTE. And, to drive home the point that the Y combinator is in there, no DEFUN, LABELS or LETREC. (Well, OK, there's an IF in there, but even that could be gotten rid of with a lazy lambda.)
I was downvoted a few times, but I actually think the line "it's just lisp" is a better response to the commenters question than any of the other comments that attempt to explain what LC is. Why explain an algorithmic construct to someone in mathematical notation, if there's an executable notation that's easier on the eyes (at least for a programmer)?