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 A031666 Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 78. 0
 13933, 123985, 124690, 126106, 185021, 258233, 260269, 262313, 347146, 550925, 553897, 559865, 679417, 823178, 953201, 957109, 959066, 962986, 964949, 966914, 972821, 974794, 1120093, 1286797, 1295885, 1467482, 1474757, 1477186 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..28. MATHEMATICA cf78Q[n_]:=Module[{s=Sqrt[n], len, cf}, cf=If[IntegerQ[s], {1, 1}, ContinuedFraction[s][[2]]]; len= Length[ cf]; OddQ[len]&&cf[[Floor[len/2]]]==cf[[Ceiling[len/2]]]==78]; Select[Range[ 1480000], cf78Q] (* Harvey P. Dale, Dec 16 2023 *) CROSSREFS Subsequence of A003814. Sequence in context: A237571 A244273 A118464 * A031819 A066939 A215150 Adjacent sequences: A031663 A031664 A031665 * A031667 A031668 A031669 KEYWORD nonn AUTHOR David W. Wilson EXTENSIONS First term 6085 removed by Georg Fischer, Jun 16 2019 STATUS approved

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Last modified July 19 21:41 EDT 2024. Contains 374436 sequences. (Running on oeis4.)