Andy Vázsonyi was a childhood friend of Paul Erdős, with whom he shared a doctoral advisor (L. Fejér) and coauthored a couple of early papers.
However Vázsonyi took an interest in applied mathematics, becoming a leader in operations research. Among the several stories he wrote about Erdős after his death is a terse account, later elaborated in the afterword to the book Erdős on Graphs, of a return to pure mathematics. He wrote:
According to Erdős a mathematician who stopped doing math was dead: he
died a most ignominious death. I was a victim of World War II so Erdős
forgave me. “Those were difficult times,” he said. But in 1960 I
proved a very difficult theorem in geometry and Erdős told Laura [Andy's wife],
“Strange, Vazsonyi is dead, but never lost the touch. Yesterday he
found a proof straight from the Big Book.”