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 A080666 Numbers n such that n^2 + 1 and n^2 - 1 are squareful. 0
 7, 41, 43, 57, 82, 93, 99, 107, 117, 118, 143, 157, 168, 193, 207, 239, 243, 251, 257, 293, 307, 327, 332, 343, 357, 368, 393, 407, 437, 443, 457, 493, 507, 515, 532, 540, 543, 557, 568, 577, 593, 606, 607, 643, 657, 693, 707, 743, 746, 757, 775, 776, 782 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This sequence is infinite. For instance, it contains all numbers of the form 100*m + 7. - Emmanuel Vantieghem, Oct 25 2016 LINKS MATHEMATICA << NumberTheory`NumberTheoryFunctions` Select[Range[10^3], ! SquareFreeQ[ #^2 - 1] && ! SquareFreeQ[ #^2 + 1] &] PROG (MAGMA) [n : n in [2..800] | not IsSquarefree(n^2-1) and not IsSquarefree(n^2+1)]; // Vincenzo Librandi, Oct 26 2016 CROSSREFS Cf. A013929. Sequence in context: A144421 A023251 A073501 * A224718 A272387 A105902 Adjacent sequences:  A080663 A080664 A080665 * A080667 A080668 A080669 KEYWORD nonn AUTHOR Joseph L. Pe, Mar 02 2003 STATUS approved

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Last modified January 19 06:37 EST 2020. Contains 331033 sequences. (Running on oeis4.)