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A028743
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Nonsquares mod 30.
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1
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2, 3, 5, 7, 8, 11, 12, 13, 14, 17, 18, 20, 22, 23, 26, 27, 28, 29
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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LINKS
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Table of n, a(n) for n=1..18.
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EXAMPLE
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Since 5 is not a perfect square and there are no solutions to x^2 = 5 mod 30, 5 is in the sequence.
Although 6 is not a perfect square either, there are solutions to x^2 = 6 mod 30, such as x = 6, x = 24, so 6 is not in the sequence.
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MATHEMATICA
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Complement[Range[30], PowerMod[Range[30], 2, 30]] (* Alonso del Arte, Nov 30 2019 *)
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PROG
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(Scala) val squaresMod30 = (1 to 30).map(n => n * n).map(_ % 30)
(0 to 29).diff(squaresMod30) // Alonso del Arte, Nov 30 2019
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CROSSREFS
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Cf. A010462.
Sequence in context: A028728 A286758 A106735 * A082634 A100959 A245303
Adjacent sequences: A028740 A028741 A028742 * A028744 A028745 A028746
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KEYWORD
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nonn,fini,full
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AUTHOR
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N. J. A. Sloane
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EXTENSIONS
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Incorrect term 15 removed by Alonso del Arte, Nov 30 2019
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STATUS
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approved
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