Richest 400 Americans' net worth jumps 13 pct to $1.7 trln-Forbes

NEW YORK, Sept 19 (Reuters) - The net worth of the richest Americans grew by 13 percent in the past year to $1.7 trillion, Forbes magazine said on Wednesday, and a familiar cast of characters once again populated the top of the magazine's annual list of the U.S. uber-elite, including Bill Gates, Warren Buffett, Larry Ellison and the Koch brothers.