Ways to get to the number Given the input of the first number and the second number (both positive integers, zero exluded), determine in how many ways could you make the second out of the first, using following actions: +1,+2 and *3. Operations are simply applied from left to right.

Examples: 


Input: 1 2. Output: 1. I.e, you could only get 2 by doing +1, so one way.
Input: 1 3. Output: 3. I.e, you could get 3 by either doing +2 or +1+1, or *3  
Input: 1 4. Output: 4.
Input: 2 6. Output: 6.
Input: 2 7. Output: 9.
Input: 1 10. Output: 84.


In case there're no ways, e.g. 100 100, or 100 80, output is 0.

You could also take input as an array, or string with any convenient separator.

The shortest solution wins.
Javascript ES6, 45 44 bytes

f=(a,b=B)=&gt;a&lt;(B=b)?f(a+1)+f(a+2)+f(a*3):a==b


Example runs:

f(1,2)  -&gt; 1
f(2,6)  -&gt; 6
f(1 10) -&gt; 84