0, 1, 2, 4, 6, 9, 12, 16, ?

0, 1, 2, 4, 6, 9, 12, 16, ?

What number should replace the question mark?

Answer:

20: add 1, 1, 2, 2, 3, 3, 4, 4.

4,4,3,3,2,2,1

Create a number using only the digits 4,4,3,3,2,2,1 and 1. So it can only be eight digits. You have to make sure the ones are separated by one digit, the twos are separated by two digits the threes are separated with three digits and the fours are separated by four digits.


 

Answer:

41312432