Question 107244
2^0+2^1+2^2+2^3...+2^67=?


this is much easier to see in binary


1111111111111111111111111111111111111111111111111111111111111111111
...is the same as...
10000000000000000000000000000000000000000000000000000000000000000000-1



(look at the source)