Don't really have time to think about this, but you can sort of generate the sum (ie by looking at the pattern) with
(1/1000) * sum i * 1000^-i , i = 0 to infinity
You could try and do a sum of a sum of geometric series and make it work
http://www.wolframalpha.com/input/?i=sum+i+*+1000%5E-i%2C+i%...
(998001 / 2997 = 3)
I had to re-read what the parent poster said to get it. So I thought I'd explain what he means when he says:
> Also, "998" doesn't appear 'in sequence' (it obviously appears as 97[9 98]0 981).
He is saying 998 is missing, as others have observed. He is also saying that if you took the string of digits and did a string search for "998", you'd obviously find those digits together in other places (specifically during the sequence of 979 980 981).
You'd also find them at 799 800 801.
It's not that people here are stuffy, or humorless, or anything; we just want HN to be different, and not decay into a festering cesspool of malfeasance like Slashdot or whatever. There are plenty of places one can go to get that kind of stuff on the 'net. Here at HN, it will usually be downvoted mercilessly.