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 A028739 Nonsquares mod 26. 1
 2, 5, 6, 7, 8, 11, 15, 18, 19, 20, 21, 24 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE Since 2 is not a perfect square and there are no solutions to x^2 = 2 mod 26, 2 is in the sequence. Although 3 is not a perfect square either, there are solutions to x^2 = 3 mod 26, such as x = 9, x = 17, 3 is not in the sequence. MATHEMATICA Complement[Range[0, 25], PowerMod[Range[0, 25], 2, 26]] (* Alonso del Arte, Nov 26 2019 *) PROG (Scala) val squaresMod26 = (0 to 25).map(n => n * n).map(_ % 26) (0 to 25).diff(squaresMod26) // Alonso del Arte, Nov 26 2019 CROSSREFS Cf. A010388. Sequence in context: A028791 A080727 A283974 * A074291 A134026 A220655 Adjacent sequences:  A028736 A028737 A028738 * A028740 A028741 A028742 KEYWORD nonn,fini,full AUTHOR EXTENSIONS Incorrect term 13 removed by Alonso del Arte, Nov 26 2019 STATUS approved

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Last modified April 12 17:17 EDT 2021. Contains 342929 sequences. (Running on oeis4.)