C=2+2²+2³+......+$2^{99}$
= (2+2³+$2^{5}$)+(2²+$2^{4}$+$2^{6}$)+.....($2^{299}$+$2^{297}$+ $2^{295}$)+($2^{300}$+$2^{298}$+$2^{296}$)
=2.(2+8+32)+2².(2+8+32)+............+$2^{95}$.(2+8+32)+$2^{296}$.(2+8+32)
=2.42+2².42+.........+$2^{95}$.42+$2^{296}$.42
=42.(2+2²+.......+$2^{95}$+$2^{296}$) ⋮ 42
Vậy C ⋮ 42