195981

The starting number can only be 1,2, and 3 so when the mode is 3 there must be more than one and other number must have less number of numbers. So to find numbers that adds up until 20 we need to find the numbers that adds up until 13, 12, and 11. Then we need to delete the numbers that repeats and that has also a number that also has more than two numbers which has the same number of 3. So we got 12 including two digit numbers.