Leibniz harmonic triangle
A triangle of fractions that is related to the more famous Pascal
triangle in a very simple way. Each row of the Leibniz harmonic triangle
starts with the reciprocal of the row number (or the row number plus one
depending on whether one starts counting from 1 or 0.) Every entry is the
sum of the two numbers just below it. The entries can thus be computed sequentially
left to right and top to bottom using subtraction instead of addition.