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

1,2

Comments

Numbers with trailing zeros are excluded.

Links

Table of n, a(n) for n=1..50.

Eric Weisstein's World of Mathematics, Square Number

Index entry for sequences related to reversing digits of squares

Formula

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

Example

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

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 *)

Crossrefs

Cf. A033294, A035125.

Sequence in context: A130803 A007932 A334054 * A085305 A189818 A116032

Adjacent sequences: A035119 A035120 A035121 * A035123 A035124 A035125

Keyword

nonn,base

Author

Patrick De Geest, Nov 15 1998

Status

approved