I started tinkering with it before reading the comments but I might as well post my thoughts. My answer was basically the same as Donald Hobson's answer except I pre-calculated the powers and factorials you would use and stored them in an array or collection, then I calculated the sum using the stored values. It's basically the same solution but a little easier to follow. If you aren't worried about breaking taboos then you could stick the factorials in a global variable and have a function to get the factorial that checks to see if the ... (read more)
I started tinkering with it before reading the comments but I might as well post my thoughts. My answer was basically the same as Donald Hobson's answer except I pre-calculated the powers and factorials you would use and stored them in an array or collection, then I calculated the sum using the stored values. It's basically the same solution but a little easier to follow. If you aren't worried about breaking taboos then you could stick the factorials in a global variable and have a function to get the factorial that checks to see if the ... (read more)