I hope this is the right place for a sequence question but I'm stuck. I can solve it programatically but not mathematically and think I'm missing something.
A series is formed with an original value of 2 and each following term in the sequence given by the previous term + the highest prime factor of the previous term so...
an+1= an + pn. The first term a1 is 2.
The series is pretty easy to construct and the following terms are the first bunch 2,4,6,9,12,15,20,25,30,35,42,49,56,63,70,77,88,99, 110,121,132,143...
The question is: What is the largest value of n such that an is a four digit number. As I said I can loop through and brute force the thing using a computer but there's got to be a pattern I'm missing.
Over to all you clever math people.