What does this mean...
(2)
(n)
where 2 an 2 are actually all n one big bracket. There is a "Sum of" sign before it.
Thank you!
no, you write the upper and lower limits of a sum on the summation sign itself, like, for example, you would write 1 and N are the lower and upper limits respectively of the sum
Now, the notation means the combination as in the combinatoric formula. it is defined as follows:
see here
so, for example, .......here the upper and lower limits are 2 and 0 respectively