观察一组数:-3,3,-9,15,-33,63,-129,256…则第N个数为

观察一组数:-3,3,-9,15,-33,63,-129,256…则第N个数为
观察一组数:-3,3,-9,15,-33,63,-129,256…则第N个数为

观察一组数:-3,3,-9,15,-33,63,-129,256…则第N个数为
-3,3,-9,15,-33,63,-129,255
第N项的2倍-第N+1项=第N+2项
N=1,2*(-3)-3=-9
N=2,2*(3)-(-9)=15
N=3,2*(-9)-15=-33
N=4,2*(15)-(-33)=63
N=5,2*(-33)-63=-129
N=6,2*(63)-(-129)=255
通项公式：an=(-1)^n*[2^(n+1)+(-1)^n]
第N个数为：(-1)^N*[2^(N+1)+(-1)^N]