A031522 - OEIS

%I #12 Feb 09 2023 17:47:39

%S 578,594,614,622,642,662,674,1299,1317,1329,1374,1389,1401,1407,1437,

%T 1461,1473,1497,1509,1518,2308,2348,2364,2372,2380,2396,2404,2412,

%U 2428,2444,2452,2460,2468,2476,2492,2508,2516,2524,2540,2564,2572,2588,2612

%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 24.

%t cf24Q[n_]:=Module[{s=Sqrt[n],cf,len},cf=If[IntegerQ[s],{1},ContinuedFraction[ s] [[2]]];len=Length[cf];EvenQ[len]&&cf[[len/2]]==24]; Select[Range[2700],cf24Q] (* _Harvey P. Dale_, Feb 09 2023 *)

%K nonn

%O 1,1

%A _David W. Wilson_