login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A031526 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 28. 0
786, 802, 822, 834, 838, 862, 866, 878, 886, 898, 1767, 1797, 1803, 1812, 1821, 1833, 1839, 1857, 1884, 1893, 1911, 1929, 1941, 1956, 1977, 1983, 2013, 2022, 3140, 3148, 3180, 3188, 3196, 3212, 3228, 3236, 3244, 3260, 3276, 3284, 3292, 3308, 3316, 3340 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..44.

MATHEMATICA

okQ[n_] := Module[{cf, p}, cf = ContinuedFraction[Sqrt[n]]; p = FindTransientRepeat[cf, 2][[1, 2]]; EvenQ[lp = Length[p]] && p[[lp/2]] == 28];

Reap[Do[If[okQ[n], Sow[n]], {n, 1, 3340}]][[2, 1]] // Quiet (* Jean-François Alcover, Dec 14 2017 *)

cf28Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {1}, ContinuedFraction[ s][[2]]]; len=Length[cf]; EvenQ[len]&&cf[[len/2]] == 28]; Select[ Range[3400], cf28Q] (* Harvey P. Dale, Jun 03 2021 *)

CROSSREFS

Sequence in context: A159896 A031734 A097776 * A108795 A097774 A031896

Adjacent sequences: A031523 A031524 A031525 * A031527 A031528 A031529

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 24 20:36 EDT 2023. Contains 361510 sequences. (Running on oeis4.)