Panel 1: The equation laid out on the ground. The kid on the right says from somewhere off the panel, "Yeah!!"
Panel 2: The equation changes to all numbers with a "ping!" now it reads, "1/1 - 1/3 + 1/5 - 1/7 +..."
The kid on the right continues to talk away from view: It's an infinite series, so you do odd number fractions
keep doing - then +
and you × 4...