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

 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.

Last modified September 24 14:54 EDT 2023. Contains 365579 sequences. (Running on oeis4.)