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%I #17 Sep 04 2023 19:26:14
%S 5627,5639,5643,5647,5651,5659,5667,5683,5711,5723,5731,5739,5743,
%T 5763,5767,5779,5783,5787,5791,5807,5827,5831,5839,5843,5851,5867,
%U 5879,5891,5899,5903,5923,5927,22504,22528,22624,22656,22688,22696,22720,22784
%N Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 75.
%C The "central term" is at period/2, not at period/2 + 1. - _Harvey P. Dale_, Feb 20 2013
%t epQ[n_]:=Module[{srt=Sqrt[n],cf,len},cf=If[IntegerQ[srt],{1},ContinuedFraction[ srt] [[2]]]; len=Length[cf];EvenQ[len]&&cf[[len/2]]==75]; Select[Range[ 23000], epQ] (* _Harvey P. Dale_, Feb 20 2013 *)
%K nonn
%O 1,1
%A _David W. Wilson_
%E Definition corrected by _Harvey P. Dale_, Sep 04 2023
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