當 f(x)=xkex,
f(n)(x)=kC0nP0xkex+kC1nP1xk-1ex+kC2nP2xk-2ex+kC3nP3xk-3ex+...+kCn-3nPn-3xk-(n-3)ex+kCn-2nPn-2xk-(n-2)ex+kCn-1nPn-1xk-(n-1)ex+kCnnPnxk-nex