A037914 a(n)=least base b>=2 such that f(b,n)>=f(b',n) for all b'>=2, where f(b,n)=number of distinct base b digits of n.

2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 4, 3, 2, 3, 2, 2, 4, 2, 2, 4, 4, 3, 4, 3, 3, 3, 3, 3, 4, 2, 3, 4, 5, 6, 3, 2, 4, 3, 3, 3, 3, 4, 4, 3, 4, 5, 4, 3, 4, 3, 3, 3, 6, 3, 6, 3, 3, 3, 3, 4, 6, 3, 4, 4, 4, 3, 4, 4, 4, 4, 4, 4, 5, 6, 4, 3, 5, 5, 3, 3, 3, 3, 6