A031625 - OEIS

A031625

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 37.

8861, 27970, 41737, 42557, 43385, 58733, 77509, 99514, 127097, 183713, 185429, 214994, 215921, 217781, 218714, 219649, 220586, 223409, 224354, 250729, 252733, 262873, 290285, 292441, 303341, 333890, 335045, 336202, 337361, 338522, 339685

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..31.

MATHEMATICA

cf37Q[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]] == 37]; Select[Range[350000], cf37Q] (* Harvey P. Dale, Jun 11 2019 *)

CROSSREFS

Sequence in context: A292572 A236031 A071564 * A046506 A116242 A116275

Adjacent sequences: A031622 A031623 A031624 * A031626 A031627 A031628

KEYWORD

nonn

AUTHOR

David W. Wilson

EXTENSIONS

Corrected and extended, and definition clarified, by Harvey P. Dale, Jun 11 2019

STATUS

approved