I'm trying to understand the generating function for OEIS A062734, which is in Mathematica. Essentially, despite knowing no Mathematica at all, I think I can parse most of it, but where do $x$ and $y$ come from?
nn = 6;
s = Sum[(1+y)^Binomial[n, 2] x^n/n!, {n, 0, nn}];
Range[0, nn]!CoefficientList[Series[Log[ s]+1, {x, 0, nn}], {x, y}]//Grid
(* returns triangle indexed at n = 0, Geoffrey Critzer, Oct 07 2012 *)
The history of the page isn't much help, and the non-Mathematica formula is very similar. Apologies for the probably completely trivial question.