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 A031404 Numbers n such that continued fraction for sqrt(n) has even period 2*m and the m-th term is 1. 20
 3, 7, 8, 15, 24, 32, 35, 48, 63, 75, 80, 88, 91, 99, 115, 120, 135, 136, 143, 168, 175, 176, 195, 208, 215, 224, 247, 255, 279, 280, 288, 304, 312, 319, 323, 360, 399, 403, 427, 432, 440, 464, 483, 528, 539, 551, 555, 560, 575, 595, 611, 624, 671, 675, 696 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS T. D. Noe, Table of n, a(n) for n = 1..1000 MATHEMATICA n = 1; t = {}; While[Length[t] < 50, n++; If[! IntegerQ[Sqrt[n]], c = ContinuedFraction[Sqrt[n]]; len = Length[c[[2]]]; If[EvenQ[len] && c[[2, len/2]] == 1, AppendTo[t, n]]]]; t (* T. D. Noe, Apr 04 2014 *) CROSSREFS Cf. A031405-A031423. Sequence in context: A045542 A249435 A192120 * A263519 A105263 A242572 Adjacent sequences:  A031401 A031402 A031403 * A031405 A031406 A031407 KEYWORD nonn AUTHOR STATUS approved

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Last modified April 10 05:04 EDT 2020. Contains 333392 sequences. (Running on oeis4.)