Expand by the binomial expansion:
Every term in that summation except the very last one
is a multiple of 68. So we separate the summation into
the summation of all the terms except the last one and
then add the last term to that:
and since
Every term in the summation is a multiple of 68, so the whole
summation is a multiple of 68, so let's label that summation as
68n, for some positive integer n.
So we have
Therefore
So the remainder when divided by 68 will be 66
Answer: 66
Edwin
