A165071 a(n) = image of n under the base-7 Kaprekar map n -> (n with digits sorted into descending order) - (n with digits sorted into ascending order)

0, 0, 0, 0, 0, 0, 0, 6, 0, 6, 12, 18, 24, 30, 12, 6, 0, 6, 12, 18, 24, 18, 12, 6, 0, 6, 12, 18, 24, 18, 12, 6, 0, 6, 12, 30, 24, 18, 12, 6, 0, 6, 36, 30, 24, 18, 12, 6, 0, 48, 48, 96, 144, 192, 240, 288, 48, 0, 48, 96, 144, 192, 240, 96, 48, 48, 96, 144, 192, 240, 144, 96, 96, 96