A037884 a(n)=(1/2)*Sum{|d(i)-e(i)|} where Sum{d(i)*7^i) is the base 7 representation of n and e(i) are the digits d(i) in nonincreasing order.

0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 0, 0, 0, 1, 2, 3, 4, 0, 0, 0, 0, 1, 2, 3, 0, 0, 0, 0, 0, 1, 2, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 0, 0, 1, 2, 3, 4, 5, 1, 1, 1, 2, 3, 4, 5, 2, 2, 2, 2, 3, 4, 5, 3, 3, 3, 3, 3, 4, 5, 4, 4, 4, 4, 4, 4, 5