A031636 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 48.

28949, 48481, 70877, 101293, 132721, 168389, 170858, 262585, 264637, 308554, 310778, 314129, 316373, 317498, 364234, 365441, 369074, 370289, 373946, 375169, 423229, 433693, 488045, 496457, 499277, 555986, 557477, 558970, 563461, 572497

Offset

1,1

Links

Table of n, a(n) for n=1..30.

Mathematica

cf48Q[n_]:=With[{s=Sqrt[n]}, {cf=If[IntegerQ[s], 1, ContinuedFraction[s][[2]]]}, {len=Length[cf]-1}, EvenQ[len]&&cf[[len/2]]==cf[[len/2+1]]==48]; Select[Range[580000], cf48Q] (* Harvey P. Dale, Dec 21 2025 *)

Crossrefs

Sequence in context: A237727 A252319 A237232 * A364720 A235820 A235817

Adjacent sequences: A031633 A031634 A031635 * A031637 A031638 A031639

Keyword

nonn

Author

David W. Wilson

Extensions

First term 2305 removed by Georg Fischer, Jun 16 2019

Status

approved