%N Numbers n whose square root contains at least one instance of n in the first n digits after the decimal point.
%C Numbers beginning with a nine are most likely to have this property, and numbers beginning with a one are least likely. No squares have it.
%H Andreas Boe, <a href="/A259571/b259571.txt">Table of n, a(n) for n = 1..551</a>
%e sqrt(17) = 4.12310562561766054... The first 17 digits after the decimal point contain "17".
%t Select[Range@ 301, ! StringFreeQ[ToString@ FromDigits@ First@ RealDigits@ N[Sqrt@ #, #], ToString@ #] &] // Rest (* _Michael De Vlieger_, Jul 02 2015 *)
%A _Andreas Boe_, Jun 30 2015