求满足C0n+C1n+2C2n+…+nCnn

S=C0n +C1n+2C2n+…+nCnn
S= nCnn+ +.+C0n
2S=(n+1)*2+n(C1n+C2n+.+C(n-1)n)
=2+n(1+C1n+C2n+.+C(n-1)n+1)
=2+n*2^n
S=1+n*2^(n-1)
试探n=9 8 7 6
n=7 S=1+7*2^6=1+64*7=1+448=449
结果：n最大7