Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #30 May 22 2022 00:01:01
%S 1,2,3,11,12,13,21,22,26,31,33,99,101,102,103,111,112,113,121,122,201,
%T 202,211,212,221,264,301,307,311,836,1001,1002,1003,1011,1012,1013,
%U 1021,1022,1031,1101,1102,1103,1111,1112,1113,1121,1122,1201,1202,1211
%N Roots of 'squares remaining square when written backwards'.
%C Numbers with trailing zeros are excluded.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/SquareNumber.html">Square Number</a>
%H <a href="/index/Sq#sqrev">Index entry for sequences related to reversing digits of squares</a>
%F a(n) = sqrt(A033294(n)). - _Michel Marcus_, Sep 22 2015
%e 99^2 = 9801 -> 1089 = 33^2.
%t Select[Range[10000], IntegerQ[Sqrt[FromDigits[Reverse[IntegerDigits[ #^2]]]]] &] (* and then delete terms ending with 0 - _N. J. A. Sloane_, Jul 08 2011 *)
%t Sqrt[Select[Range[2000]^2, Mod[#, 10]!=0&&IntegerQ[Sqrt[FromDigits[Reverse[IntegerDigits[#]]]]]&]] (* _Vincenzo Librandi_, Sep 22 2015 *)
%Y Cf. A033294, A035125.
%K nonn,base
%O 1,2
%A _Patrick De Geest_, Nov 15 1998