This Is Out Of Box Thinking!

Why it was needed?

I said earlier this needs some out of box thinking.

If you carefully observe the digits in the series you won't find any digit exceeding 7 or 8. From that you have to conclude the series must be in octal (number system to base 7 is uncommon).

The series can be represented as,

(x + 1) ^2    ...........where x varies from 0,1,2,3,4,5,6,7,10........

And it's in octal number system.

Out of Box Thought

So the answer is 241.