The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A031606 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 18. 0
 82, 2141, 4274, 6970, 7306, 10525, 10937, 14569, 15053, 18994, 20389, 24314, 25253, 25889, 30637, 31337, 36541, 43793, 47618, 51701, 52154, 52609, 53066, 54449, 55381, 62233, 70537, 71597, 72665, 80485, 81050, 82757, 83905, 85061, 85642, 86225, 86810 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..37. MATHEMATICA opct18Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {0, 0}, ContinuedFraction[s][[2]]]; len=Length[cf]; OddQ[len] && cf[[(len+1)/2]] == 18]; Select[Range[90000], opct18Q] (* Harvey P. Dale, Nov 12 2013 *) CROSSREFS Subsequence of A003814. Sequence in context: A280857 A281603 A234253 * A232904 A230395 A017798 Adjacent sequences: A031603 A031604 A031605 * A031607 A031608 A031609 KEYWORD nonn AUTHOR David W. Wilson EXTENSIONS Corrected by Harvey P. Dale, Nov 12 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 27 23:16 EDT 2024. Contains 372900 sequences. (Running on oeis4.)