the man who loved numbers (4) a frenzied pace

In a never-ending good mathematical problems and fresh mathematical talent, Erdös criss-crossed four continents at a , moving from one university or research centre to the next.

His was to show up on the doorstep of a fellow mathematician, declare "My brain is open", work with his host for a day or two, until he was bored or his host was , and then move on to another home. Erdös's motto was not "Other cities, other maidens" but "Another roof, another proof".

Erdös first did mathematics at the age of three, but for the last 25 years of his life, since the death of his mother, he 19-hour days, going with 10 to 20 milligrams of Benzedrine or Ritalin, strong espresso and caffeine tablets.

"A mathematician," Erdös was saying, "is a machine coffee into theorems." When friends urged him to slow down, he always had the same response: "There'll be plenty of time to rest in the grave."

Erdös would let nothing stand in mathematical progress. When the name of a colleague in California at breakfast in New Jersey, Erdös remembered a mathematical result he wanted to share with him. He the phone and started to dial. His host interrupted him, that it was 5am on the West Coast. "Good," said Erdös, "that means he'll be home."

"Erdös had a childlike tendency to make his reality ," said one colleague. "And he wasn't an easy house guest. But we all wanted him around - for his mind. We all problems for him."