Hey John,

Suppose I have the sequence \$1,1,2,4,7,13,24,...\$

These are the [*Tribonacci Numbers*](http://mathworld.wolfram.com/TribonacciNumber.html) or [A000073](https://oeis.org/A000073) in the OEIS.

This is given by the recurrence

\$x_{n} = x_{n-1} + x_{n-2} + x_{n-3} \$

I know a matrix that I can use to compute the *n*th digit of this in \$$\mathcal{O}(ln(n))\$$.

How would you make a matrix to represent this recurrence?

(I'm asking as a novice turning to a master. I think my solution has some reduction applied that makes the graph connection less clear.)