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 A031662 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 74. 0

%I #16 Aug 18 2021 00:10:32

%S 1370,12553,34621,111637,166585,169865,312706,400978,403514,501625,

%T 504461,611965,728138,731554,743573,858101,859954,861809,867386,

%U 869249,872981,876721,1158617,1162925,1167241,1171565,1180237,1323461,1328065,1332677,1339610

%N 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 74.

%t cf74Q[n_]:=Module[{s=Sqrt[n],cf,len},cf=If[IntegerQ[s],{2,2}, ContinuedFraction[ s][[2]]];len=Length[cf];OddQ[len] && cf[[(len+1)/2]]==74]; Select[Range[1400000],cf74Q] (* _Harvey P. Dale_, Mar 15 2015 *)

%K nonn

%O 1,1

%A _David W. Wilson_

%E Definition clarified and terms corrected and extended by _Harvey P. Dale_, Mar 15 2015

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Last modified September 25 13:12 EDT 2023. Contains 365647 sequences. (Running on oeis4.)