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A128921 Palindromes m such that reverse of m^2 is also a square.

%I A128921 #16 Jul 29 2023 06:41:44
%S A128921 0,1,2,3,11,22,33,99,101,111,121,202,212,1001,1111,2002,10001,10101,
%T A128921 10201,11011,11111,11211,20002,20102,100001,101101,110011,111111,
%U A128921 200002,1000001,1001001,1002001,1010101,1011101,1012101,1100011,1101011
%N A128921 Palindromes m such that reverse of m^2 is also a square.
%C A128921 Most terms have a palindromic square; for the rare exceptions see A133901. - _Klaus Brockhaus_ and _Zak Seidov_, Sep 29 2007
%H A128921 Klaus Brockhaus, <a href="/A128921/b128921.txt">Table of n, a(n) for n = 1..360</a>
%e A128921 33 and 99 are terms because 33^2=1089 => 9801=99^2 and 99^2=9801 => 1089=33^2.
%t A128921 A128921=Select[Range[0, 100000], IntegerQ[Sqrt[FromDigits[Reverse[IntegerDigits[ #^2 ]]]]]&&FromDigits[Reverse[IntegerDigits[ # ]]]==#&]
%o A128921 (Python)
%o A128921 from sympy.ntheory.primetest import is_square
%o A128921 from itertools import chain, count, islice
%o A128921 def A128921_gen(): # generator of terms
%o A128921     return filter(lambda n:is_square(int(str(n**2)[::-1])),chain((0,),chain.from_iterable(chain((int((s:=str(d))+s[-2::-1]) for d in range(10**l,10**(l+1))), (int((s:=str(d))+s[::-1]) for d in range(10**l,10**(l+1)))) for l in count(0))))
%o A128921 A128921_list = list(islice(A128921_gen(),20)) # _Chai Wah Wu_, Jun 23 2022
%Y A128921 Cf. A002113, A057135, A057136, A133901.
%K A128921 nonn,base,easy
%O A128921 1,3
%A A128921 _Zak Seidov_, Mar 02 2005, definition corrected Sep 16 2007
%E A128921 More terms from _Klaus Brockhaus_, Sep 23 2007