What is Pascal's triangle?
Pascal's triangle is a triangle of numbers bordered by ones on the right and left sides. Every number inside the triangle is the sum of the two numbers above it.
You can use Pascal's triangle to predict the intensity ratios of proton NMR multiplets.
Thus, an AX doublet has 1:1 or equal intensities. An AX₂ triplet has intensity ratios of 1:2:1. An AX₃ quartet has 1:3:3:1 ratios, etc.