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A035090 Non-palindromic squares which when written backwards remain square (and still have the same number of digits). 8
144, 169, 441, 961, 1089, 9801, 10404, 10609, 12544, 12769, 14884, 40401, 44521, 48841, 90601, 96721, 1004004, 1006009, 1022121, 1024144, 1026169, 1042441, 1044484, 1062961, 1212201, 1214404, 1216609, 1236544, 1238769, 1256641 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Squares with trailing zeros not included.

Sequence is infinite, since it includes e.g. 10^(2k)+4*10^k+4 for all k. - Robert Israel, Sep 20 2015

LINKS

Robert Israel, Table of n, a(n) for n = 1..798

P. De Geest, Palindromic Squares

Index entry for sequences related to reversing digits of squares

FORMULA

a(n) = A035123(n)^2. - R. J. Mathar, Jan 25 2017

MAPLE

rev:= proc(n) local L, i;

L:= convert(n, base, 10);

add(L[-i]*10^(i-1), i=1..nops(L))

end proc:

filter:= proc(n) local t;

  if n mod 10 = 0 then return false fi;

  t:= rev(n);

t <> n and issqr(t)

end proc:

select(filter, [seq(n^2, n=1..10^5)]); # Robert Israel, Sep 20 2015

CROSSREFS

Reversing a polytopal number gives a polytopal number:

cube to cube: A035123, A035124, A035125, A002781;

square to square: A161902, A035090, A033294, A106323, A106324, A002779;

square to triangular: A181412, A066702;

tetrahedral to tetrahedral: A006030;

triangular to square: A066703, A179889;

triangular to triangular: A066528, A069673, A003098, A066569.

Cf. A319388.

Sequence in context: A085426 A034289 A062917 * A064021 A156316 A245214

Adjacent sequences:  A035087 A035088 A035089 * A035091 A035092 A035093

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Nov 15 1998

STATUS

approved

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Last modified November 15 09:36 EST 2018. Contains 317232 sequences. (Running on oeis4.)