Possible Clues:

• Graduates penning article pronounced artist to be calculating individual
• Ham can imitate cast in summer
• Describing this puzzle, one across in person?
• Eg, Leonhard Euler
• Incite Mahatma to riot -- he's calculating type
• A man wrestling with arithmetic — not reading or writing?
• Dealer in numbers
• With a subject, one has a boring fellow that's an expert in one
• Bertrand Russell, for one
• Eg, Euclid, Fermat or seven down