Triple Product (noch nicht übersetzt)

Problem 831

Let g(m) be the integer defined by the following double sum of products of binomial coefficients:

mj=0ji=0(1)ji(mj)(ji)(j+5+6ij+5)

You are given that g(10)=127278262644918.
Its first (most significant) five digits are 12727.
Find the first ten digits of g(142857) when written in base 7.