O(n^[number]) = polynomial, with O(n^2) being quadratic.
O([a number]^n) = exponential.
I guess the authors aren't big on CS fundamentals?
Indeed. It's been a while since I've had to so much as think about big O notation and I forgot that quirk. To most folks "exponential" means n^2 or greater
“Superlinear” is the word you’re looking for.
Superlinear can mean O(n log n) or anything like that, which is smaller than O(n^2).