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%I #12 Aug 18 2021 00:10:32
%S 52009,169825,170650,252125,350633,466714,474946,600914,604018,605573,
%T 757261,760745,914377,925885,929737,1098833,1103029,1109338,1113554,
%U 1117778,1297946,1302506,1304789,1313941,1316234,1318529,1320826
%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 91.
%t cf91Q[n_]:=Module[{s=Sqrt[n],cf,len},cf=If[IntegerQ[s],{1,1}, ContinuedFraction[ s][[2]]];len=Length[cf];OddQ[len]&&cf[[(len+1)/2]] == 91]; Select[Range[14*10^5],cf91Q] (* _Harvey P. Dale_, Sep 23 2018 *)
%K nonn
%O 1,1
%A _David W. Wilson_
%E Corrected by _Harvey P. Dale_, Sep 23 2018
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