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A035090 Non-palindromic squares which when written backwards remain square (and still have the same number of digits). 12


%S 144,169,441,961,1089,9801,10404,10609,12544,12769,14884,40401,44521,

%T 48841,90601,96721,1004004,1006009,1022121,1024144,1026169,1042441,

%U 1044484,1062961,1212201,1214404,1216609,1236544,1238769,1256641

%N Non-palindromic squares which when written backwards remain square (and still have the same number of digits).

%C Squares with trailing zeros not included.

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

%H Robert Israel, <a href="/A035090/b035090.txt">Table of n, a(n) for n = 1..798</a>

%H P. De Geest, <a href="http://www.worldofnumbers.com/square.htm">Palindromic Squares</a>

%H <a href="/wiki/Index_to_OEIS:_Section_Sq#sqrev">Index entry for sequences related to reversing digits of squares</a>

%F a(n) = A035123(n)^2. - _R. J. Mathar_, Jan 25 2017

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

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

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

%p end proc:

%p filter:= proc(n) local t;

%p if n mod 10 = 0 then return false fi;

%p t:= rev(n);

%p t <> n and issqr(t)

%p end proc:

%p select(filter, [seq(n^2, n=1..10^5)]); # _Robert Israel_, Sep 20 2015

%Y Reversing a polytopal number gives a polytopal number:

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

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

%Y square to triangular: A181412, A066702;

%Y tetrahedral to tetrahedral: A006030;

%Y triangular to square: A066703, A179889;

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

%Y Cf. A319388.

%K nonn,base

%O 1,1

%A _Patrick De Geest_, Nov 15 1998

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Last modified December 8 01:46 EST 2019. Contains 329850 sequences. (Running on oeis4.)