1/2+1/6+1/12+...+1/n(n+1)=2003/2004
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+...+(1/n-1/(n+1))
=1-1/2+1/2-1/3+1/3-1/4+...+1/n-1/(n+1)
=1-1/(n+1)
=n/(n+1)
=2003/2004
所以n=2003
1/2+1/6+1/12+...+1/n(n+1)=2003/2004
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+...+(1/n-1/(n+1))
=1-1/2+1/2-1/3+1/3-1/4+...+1/n-1/(n+1)
=1-1/(n+1)
=n/(n+1)
=2003/2004
所以n=2003