(2²+1)(2^4+1)(2^8+1)(2^16+1)=(2²-1)(2²+1)(2^4+1)(2^8+1)(2^16+1)/(2²-1)=(2^4-1)(2^4+1)(2^8+1)(2^16+1)/3=(2^8-1)(2^8+1)(2^16+1)/3=(2^16-1)(2^16+1)/3=(2^32-1)/3