How to use Power with NumberForm?

Question

Being in need of calculating the following numbers with 18 decimals of precision: $2^{2^{-x}}, x\in{\mathbb{N}}$.

I looked for what built-in symbols can help me and found Power and NumberForm. I tried an example:

NumberForm[Power[2, 2^-3], 18]

But when evaluated, it shows up like $2^{1/8}$, whereas I wanted $1.090507732665257659$. How can I make WolframCloud use the latter formatting?

Answer 1

I figured it out shortly after posting the question. I should have used the N built-in symbol rather than NumberForm. Rewriting the code snippet to make it work:

N[Power[2, 2^-3], 18]

I may have been able to keep using NumberForm if I wanted to by wrapping the Power[...] expression within N, but it looks like N suffices for I needed to do.