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A102859 Numbers that when squared and written backwards give a square again.

%I A102859 #24 Nov 19 2022 00:53:45
%S A102859 0,1,2,3,10,11,12,13,20,21,22,26,30,31,33,99,100,101,102,103,110,111,
%T A102859 112,113,120,121,122,130,200,201,202,210,211,212,220,221,260,264,300,
%U A102859 301,307,310,311,330,836,990,1000,1001,1002,1003,1010,1011,1012,1013,1020
%N A102859 Numbers that when squared and written backwards give a square again.
%C A102859 Contains A002778. - _Robert Israel_, Sep 20 2015
%C A102859 Squares of these terms are in A061457. - _Jon E. Schoenfield_, May 17 2022
%H A102859 Jon E. Schoenfield, <a href="/A102859/b102859.txt">Table of n, a(n) for n = 1..10000</a>
%H A102859 <a href="/index/Sq#sqrev">Index entry for sequences related to reversing digits of squares</a>
%F A102859 a(n) = sqrt(A061457(n)). - _Jon E. Schoenfield_, May 17 2022
%e A102859 a(7)=12 belongs to the sequence since writing 12^2 = 144 backwards gives 441 = 21^2.
%p A102859 rev:= proc(n)
%p A102859   local L, Ln, i;
%p A102859   L:= convert(n, base, 10);
%p A102859   Ln:= nops(L);
%p A102859   add(L[i]*10^(Ln-i), i=1..Ln);
%p A102859 end proc:
%p A102859 select(t -> issqr(rev(t^2)),[$0..10^5]); # _Robert Israel_, Sep 20 2015
%t A102859 Select[Range[1000], IntegerQ[Sqrt[FromDigits[Reverse[IntegerDigits[ #^2]]]]] &]
%o A102859 (Magma) [n: n in [0..1100] | IsSquare(Seqint(Reverse(Intseq(n^2))))]; // _Vincenzo Librandi_, Sep 21 2015
%o A102859 (Python)
%o A102859 from itertools import count, islice
%o A102859 from sympy import integer_nthroot
%o A102859 def A102859_gen(startvalue=0): # generator of terms >= startvalue
%o A102859     return filter(lambda n:integer_nthroot(int(str(n**2)[::-1]),2)[1], count(max(startvalue,0)))
%o A102859 A102859_list = list(islice(A102859_gen(),30)) # _Chai Wah Wu_, Nov 18 2022
%Y A102859 Cf. A002778, A002942.
%Y A102859 Cf. A061457 (squares).
%K A102859 base,easy,nonn
%O A102859 1,3
%A A102859 Sanita Kashcheyeva (sanits(AT)gmail.com), Mar 01 2005
%E A102859 0 inserted by _Jon E. Schoenfield_, Sep 20 2015