I have a problem solving coding challenge when I have to calculate the number of combinations, numbers from **0** to **9**, with the length **n**, with **2** rules –

**–** The first number cannot be **0**

**–** Every other number can be **0** or must be divisible by the previous number (number **1** can not be used as divisor), for example **[5.0], [1,0]** or **[2,8], [4,8], [3,6]**

For example, if the length **n** were **2**, number of combinations would be **21 – [1,0]…[9,0] + [2,4], [2,6], [2,8], [3,6], [3,9], [4,8] + [2,2]…[9,9]**

The resulting response can be code in some programming language or a formula to calculate answer