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

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A031667 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 79. 0
39229, 128245, 191965, 268493, 355441, 357829, 451873, 458618, 565865, 568877, 571897, 689341, 832273, 843253, 976769, 984689, 986674, 988661, 992641, 994634, 996629, 998626, 1149913, 1327945, 1332557, 1504037, 1508945, 1513861, 1526186, 1531130, 1536082 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

MATHEMATICA

op79Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {1, 1}, ContinuedFraction[ s][[2]]]; len=Length[cf]; OddQ[len] && cf[[Floor[ len/2]+1]] == 79]; Select[Range[1600000], op79Q] (* Harvey P. Dale, Aug 04 2013 *)

CROSSREFS

Sequence in context: A224622 A233955 A250515 * A196200 A274128 A144306

Adjacent sequences:  A031664 A031665 A031666 * A031668 A031669 A031670

KEYWORD

nonn

AUTHOR

David W. Wilson

EXTENSIONS

Corrected and extended by Harvey P. Dale, Aug 04 2013

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 December 5 10:11 EST 2021. Contains 349543 sequences. (Running on oeis4.)