usage = "
The Division String Problem: (David M. Sanger)
Find a maximal integer a_1 a_2 ... a_t, consisting of t decimal digits
a_1 , a_2 , ... , a_t (also with t maximal), such that a_1 a_2 ... a_i
is divisible by i, for i=1,2,3,...,t , or show that there is no upper bound
for the collection of these integers.
Equidistribution Heuristic:
Let D(n) be division strings of length n except the all zero string.
Assuming that a(n,i) = { x in D(n-1) with x mod n = i } are nearly
equal for all i with 0<=i