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A102859
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Numbers that when squared and written backwards give a square again.
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7
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0, 1, 2, 3, 10, 11, 12, 13, 20, 21, 22, 26, 30, 31, 33, 99, 100, 101, 102, 103, 110, 111, 112, 113, 120, 121, 122, 130, 200, 201, 202, 210, 211, 212, 220, 221, 260, 264, 300, 301, 307, 310, 311, 330, 836, 990, 1000, 1001, 1002, 1003, 1010, 1011, 1012, 1013, 1020
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OFFSET
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1,3
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COMMENTS
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Contains A002778. - Robert Israel, Sep 20 2015
Squares of these terms are in A061457. - Jon E. Schoenfield, May 17 2022
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LINKS
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Jon E. Schoenfield, Table of n, a(n) for n = 1..10000
Index entry for sequences related to reversing digits of squares
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FORMULA
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a(n) = sqrt(A061457(n)). - Jon E. Schoenfield, May 17 2022
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EXAMPLE
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a(7)=12 belongs to the sequence since writing 12^2 = 144 backwards gives 441 = 21^2.
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MAPLE
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rev:= proc(n)
local L, Ln, i;
L:= convert(n, base, 10);
Ln:= nops(L);
add(L[i]*10^(Ln-i), i=1..Ln);
end proc:
select(t -> issqr(rev(t^2)), [$0..10^5]); # Robert Israel, Sep 20 2015
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MATHEMATICA
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Select[Range[1000], IntegerQ[Sqrt[FromDigits[Reverse[IntegerDigits[ #^2]]]]] &]
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PROG
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(Magma) [n: n in [0..1100] | IsSquare(Seqint(Reverse(Intseq(n^2))))]; // Vincenzo Librandi, Sep 21 2015
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CROSSREFS
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Cf. A002778, A002942.
Cf. A061457 (squares).
Sequence in context: A055655 A276326 A007090 * A069967 A061909 A345358
Adjacent sequences: A102856 A102857 A102858 * A102860 A102861 A102862
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KEYWORD
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base,easy,nonn
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AUTHOR
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Sanita Kashcheyeva (sanits(AT)gmail.com), Mar 01 2005
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EXTENSIONS
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0 inserted by Jon E. Schoenfield, Sep 20 2015
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STATUS
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approved
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