(a+1)(a^2+1)(a^4+1)……(a^64+1)
=(a-1)(a+1)(a^2+1)……(a^64+1)/(a-1)
=(a^2-1)(a^2+1)……(a^64+1)/(a-1)
=(a^4-1)*.....(a^64+1)/(a-1)
.........
=(a^64-1)(a^64+1)/(a-1)
=(a^128-1)/(a-1)
(a+1)(a^2+1)(a^4+1)……(a^64+1)
=(a-1)(a+1)(a^2+1)……(a^64+1)/(a-1)
=(a^2-1)(a^2+1)……(a^64+1)/(a-1)
=(a^4-1)*.....(a^64+1)/(a-1)
.........
=(a^64-1)(a^64+1)/(a-1)
=(a^128-1)/(a-1)