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A128921
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Palindromes m such that reverse of m^2 is also a square.
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4
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0, 1, 2, 3, 11, 22, 33, 99, 101, 111, 121, 202, 212, 1001, 1111, 2002, 10001, 10101, 10201, 11011, 11111, 11211, 20002, 20102, 100001, 101101, 110011, 111111, 200002, 1000001, 1001001, 1002001, 1010101, 1011101, 1012101, 1100011, 1101011
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OFFSET
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1,3
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COMMENTS
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LINKS
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EXAMPLE
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33 and 99 are terms because 33^2=1089 => 9801=99^2 and 99^2=9801 => 1089=33^2.
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MATHEMATICA
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A128921=Select[Range[0, 100000], IntegerQ[Sqrt[FromDigits[Reverse[IntegerDigits[ #^2 ]]]]]&&FromDigits[Reverse[IntegerDigits[ # ]]]==#&]
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PROG
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(Python)
from sympy.ntheory.primetest import is_square
from itertools import chain, count, islice
def A128921_gen(): # generator of terms
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))))
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CROSSREFS
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KEYWORD
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nonn,base,easy
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AUTHOR
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Zak Seidov, Mar 02 2005, definition corrected Sep 16 2007
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EXTENSIONS
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STATUS
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approved
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