Necessary Integers, Tri-Friendly Numbers

Although this expression is enclosed in a square root, substituting a positive integer for n always results in an integer. I devised this formula myself; although its name includes “trifriends,” it is an application of “difriends.” I have created a separate formula for difriends. Furthermore, since it was designed to be used in conjunction with difriends, I think it would be rather dull to use it on its own.