login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A031672 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 84. 0
1765, 143722, 144481, 215417, 405994, 511514, 514378, 515813, 518689, 781897, 796105, 941429, 947258, 951154, 1105226, 1122106, 1126346, 1304893, 1494125, 1499017, 1508825, 1513741, 1711825, 1714442, 1730186, 1732817, 1927633, 1933189, 1941538 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..29.

MATHEMATICA

cf84Q[n_]:=Module[{s=Sqrt[n], c, len}, c=If[IntegerQ[s], {0, 0}, ContinuedFraction[ s][[2]]]; len=Length[c]; OddQ[len]&&c[[(len+1)/2]] == 84]; Select[Range[2*10^6], cf84Q] (* Harvey P. Dale, Jul 31 2016 *)

CROSSREFS

Sequence in context: A343989 A343988 A031762 * A031540 A135795 A206201

Adjacent sequences:  A031669 A031670 A031671 * A031673 A031674 A031675

KEYWORD

nonn

AUTHOR

David W. Wilson

EXTENSIONS

Corrected and extended by Harvey P. Dale, Jul 31 2016

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 18 19:15 EDT 2021. Contains 348069 sequences. (Running on oeis4.)