I'm doing some research on algorithms complexity and in different papers I notice both the use of the regular Big-O operator O(...) and a variant O*(...).
I never saw the definition of the latter one, which has an asterisk. I can't seem to find a definition anywhere. (Disclaimer: Googling for symbols is nearly impossible.)
What is the name and definition of the O*(...) operator? And how does it differ from the regular Big-O operator?