2004^2-2003^2+2002^2-2001^2+...+2^2-1
=(2004+2003)(2004-2003)+(2002+2001)(2002-2001)+……+(2+1)(2-1)
=2004+2003+2002+2001+……+2+1
=(1+2004)×2004/2
=2009010
(2-1)(2+1)(2^2+1)(2^4+1)...(2^2^n+1)
=(2^2-1)(2^2+1)(2^4+1)...(2^2^n+1)
=(2^4-1)(2^4+1)...(2^2^n+1)
=2^2^(n+1)-1