trapezoidal numbers!?

Question

3.can powers of 2 be trapezoidal numbers?

Justify your answer.

4. Which numbers can be represented as trapezoids with
- two addends?
-three addends?
-'n' addends

Answer 1

A trapezoidal number can be represented by the Gaussian
Arithmetic sequence sum:

S =n(a + (n-1)/2)

In order for this to be a power of 2, both n and (a+(n-1)/2) must be powers of 2. But if n is a power of 2, then a+(n-1)/2 must be a fraction (not a power of 2).

Answer 2

I really have no idea about maths questions.