login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A102859 Numbers that when squared and written backwards give a square again. 7
0, 1, 2, 3, 10, 11, 12, 13, 20, 21, 22, 26, 30, 31, 33, 99, 100, 101, 102, 103, 110, 111, 112, 113, 120, 121, 122, 130, 200, 201, 202, 210, 211, 212, 220, 221, 260, 264, 300, 301, 307, 310, 311, 330, 836, 990, 1000, 1001, 1002, 1003, 1010, 1011, 1012, 1013, 1020 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Contains A002778. - Robert Israel, Sep 20 2015

Squares of these terms are in A061457. - Jon E. Schoenfield, May 17 2022

LINKS

Jon E. Schoenfield, Table of n, a(n) for n = 1..10000

Index entry for sequences related to reversing digits of squares

FORMULA

a(n) = sqrt(A061457(n)). - Jon E. Schoenfield, May 17 2022

EXAMPLE

a(7)=12 belongs to the sequence since writing 12^2 = 144 backwards gives 441 = 21^2.

MAPLE

rev:= proc(n)

  local L, Ln, i;

  L:= convert(n, base, 10);

  Ln:= nops(L);

  add(L[i]*10^(Ln-i), i=1..Ln);

end proc:

select(t -> issqr(rev(t^2)), [$0..10^5]); # Robert Israel, Sep 20 2015

MATHEMATICA

Select[Range[1000], IntegerQ[Sqrt[FromDigits[Reverse[IntegerDigits[ #^2]]]]] &]

PROG

(Magma) [n: n in [0..1100] | IsSquare(Seqint(Reverse(Intseq(n^2))))]; // Vincenzo Librandi, Sep 21 2015

CROSSREFS

Cf. A002778, A002942.

Cf. A061457 (squares).

Sequence in context: A055655 A276326 A007090 * A069967 A061909 A345358

Adjacent sequences:  A102856 A102857 A102858 * A102860 A102861 A102862

KEYWORD

base,easy,nonn

AUTHOR

Sanita Kashcheyeva (sanits(AT)gmail.com), Mar 01 2005

EXTENSIONS

0 inserted by Jon E. Schoenfield, Sep 20 2015

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 15 15:31 EDT 2022. Contains 356148 sequences. (Running on oeis4.)