#4
^^
That IS the formula for the scale, but it's not a scale in the same sense that the major scale is one. It's formed by basing a minor pentatonic and major pentatonic scale from the same root, and that gives the intervals from the formula above, but the real 'sound' of the scale is created by switching back and forth between the two pentatonics. If you try to shred using it, you're just going to end playing something highly chromatic that won't sound anything like the blues.

People like Clapton, Hendrix, Van Halen, SRV, along with many blues, country (real country, not pop-country), and bluegrass guitarists play it. You might hear it in jazz or fusion as well, but probably not as often.
known as Jeff when it really matters
#5
^You hear it in a lot of jazz blues tunes, like Blue Monk.