Arduino pow() making 9's
I put this code into the IDE, and for n>=2, I got 99, 999, 9999 etc. The catch is that Arduino uses floating point arithmetic to implement the pow() function, and some of your values are being truncated as ints. If you change:

   int multiplier = pow(10,power);


to 

   float multiplier = pow(10,power);


The results should be as expected.

(The brief reason why floats are used is related to the fact that it is very easy to calculate the pow() function using logs, and this makes it easy to pow() non-integers too. This also means that it may not be as exact as you would hope).