7 ervoor dan 1 erachter

$\eqalign{ & 7776 = 16 \cdot 486 \cr & 77776 = 16 \cdot 4861 \cr & 777776 = 16 \cdot 48611 \cr & 7777776 = 16 \cdot 486111 \cr & 77777776 = 16 \cdot 4861111 \cr & 777777776 = 16 \cdot 48611111 \cr & ... \cr}$

Maar ja... wat dan?:-)

$\eqalign{ & \,\,\,\,\,\,48611111 \cr & \underline {\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,16\,} \, \times \cr & \,\,\,291666666 \cr & \underline {\,\,\,48611111\,\,\,\,} \,\,\, + \cr & \,\,\,777777776 \cr}$ 

Of ook: 777777777777777776 is deelbaar door 16.