(5+1)(5²+1)(5的四次方+1)（5的八次方+1)......(5的六十四次方+1）+1/4

原式=1/4*(5-1)(5+1)(5^2+1)……(5^64+1)+1/4 =1/4*(5^2-1)(5^2+1)……(5^64+1)+1/4 =…… =1/4*(5^128-1)+1/4 =(5^128)/4 另解 (5+1)(5^2+1)(5^4+1)（5^8+1)……(5^64+1）的展开式恰好是 1+5+5^2+5^3+5^4+……+5^127