The sequence 2, 3, 5, 6, 7, 10, 11, contains all the positive integers from least to greatest that are neither squares nor cubes. What is the \(400^{\mathrm{th}}\) term of the sequence?

Logic
Oct 12, 2018

#1**+1 **

I'm seeing it's 425.

I don't have a suggestion on how to find that though.

I guess you could start at 400 and add 1 for every square or cube you encounter in the list

There are 20 squares <= 400, 1-20,

There are 7 cubes <= 400, 1-7

But you seem to be excluding 1 from the series and that's counted here twice so we only have 25 squares and cubes.

Thus the 400th element is 425.

Rom
Oct 12, 2018