okay.
Number Repeating Cycle of Sum of Digits of Multiples
2 {2,4,6,8,1,3,5,7,9}
3 {3,6,9,3,6,9,3,6,9}
4 {4,8,3,7,2,6,1,5,9}
5 {5,1,6,2,7,3,8,4,9}
6 {6,3,9,6,3,9,6,3,9}
7 {7,5,3,1,8,6,4,2,9}
8 {8,7,6,5,4,3,2,1,9}
9 {9,9,9,9,9,9,9,9,9}
10 {1,2,3,4,5,6,7,8,9}
11 {2,4,6,8,1,3,5,7,9}
12 {3,6,9,3,6,9,3,6,9}
13 {4,8,3,7,2,6,1,5,9}
It is asserted that the sum of digits follows a repeating sequence of length 9. This is so because for any decimal representation x, the number 10*x (ten times x) will have the same sum of digits. Multiplication by the base number 10 simply moves the digits one place to the left and puts a zero in the units place. More generally,