[cperciva]

In a sense this is d/d{primes}. D(8) is how fast 8 changes with respect to 2, while D(60) is how fast 60 changes if 2, 3, and 5 simultaneously increase (at the same rate).

[e12e]

So... we can use it to determine the age of the universe, if we know at which point in time 6 * 9 = 42 held, by extrapolating back to at what point 6 * 9 = 0? ;-)

[ed: looks like my multiplication signs got eaten by hn]