Hi Everyone,

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...

a_{n+1}= a_{n}+ p_{n}. The first term a_{1}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 a_{n }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.

Cheers