%N Numbers n such that n and its 10's complement are both squares, i.e., n and 10^k - n (where k is the number of digits in n) are squares.
%C Terms from V. P. Singh. If k in sequence so is k * 100^m. See A068075 for the smaller of the primitive pairs.
%e 324 = 18^2 is a member as 1000 - 324 = 676 = 26^2.
%t Select[Range[10^4]^2, IntegerQ[Sqrt[10^(IntegerLength[#]) - #]] &] (* _Jayanta Basu_, Aug 05 2013 *)
%Y Cf. A068075.
%A _Amarnath Murthy_, Mar 07 2002
%E Edited and extended by _Robert G. Wilson v_, Mar 20 2002