Question

0,1,3,6,10,15,25,40,65,105 in set builder​

Answer 1

Answer:

I have tried to create the set builder of this infinite set:

0, 1, 3, 6, 10, 15, 21, 28,...

I have notice that

n=(n−1)+(N+1)

where n is the current number, n - 1 is the previous number and N + 1 is a natural number which represents the number of numbers before n.

For example, suppose n=3

3 = 1 + 2

The problem is that I do not know how to really represent N-1, because, if we do not know how many numbers that are before n, we cannot find N+1 and therefore n.