The positive integers are bracketed as follows:
(1), (2,3), (4,5,6), . . .
where there are r integers in the rth bracket. Prove that the sum of the integers in the rth bracket is
this is what I did
using the formula for arithmetic sequence,
we know that there are r integers. and the difference is 1
so that becomes
Sum of r integers = where a is the first term of the sequence
However, I can't figure out what a (a.k.a the first term) is equal to
any ideas?
thanks