A035122 Roots of 'squares remaining square when written backwards'.

1, 2, 3, 11, 12, 13, 21, 22, 26, 31, 33, 99, 101, 102, 103, 111, 112, 113, 121, 122, 201, 202, 211, 212, 221, 264, 301, 307, 311, 836, 1001, 1002, 1003, 1011, 1012, 1013, 1021, 1022, 1031, 1101, 1102, 1103, 1111, 1112, 1113, 1121, 1122, 1201, 1202, 1211

Offset: 1

Author

Patrick De Geest, Nov 15 1998

Keywords

• nonn
• base

Comments

Numbers with trailing zeros are excluded.

Examples

			99^2 = 9801 -> 1089 = 33^2.
		

Links

• Eric Weisstein's World of Mathematics, Square Number
• Index entry for sequences related to reversing digits of squares

Crossrefs

Cf. A033294, A035125.

Programs

Mathematica

Select[Range[10000], IntegerQ[Sqrt[FromDigits[Reverse[IntegerDigits[ #^2]]]]] &] (* and then delete terms ending with 0 - N. J. A. Sloane, Jul 08 2011 *)
Sqrt[Select[Range[2000]^2, Mod[#, 10]!=0&&IntegerQ[Sqrt[FromDigits[Reverse[IntegerDigits[#]]]]]&]] (* Vincenzo Librandi, Sep 22 2015 *)

Formula

a(n) = sqrt(A033294(n)). - Michel Marcus, Sep 22 2015