|
|
A031615
|
|
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 27.
|
|
0
|
|
|
4649, 9458, 15457, 15706, 22621, 31853, 32569, 41434, 53189, 54113, 56458, 66925, 67961, 81097, 82237, 99754, 101653, 102929, 114869, 115546, 116906, 118274, 121034, 121729, 122426, 137629, 154505, 160841, 162445, 164057, 175685, 176522, 178202, 179890
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
LINKS
|
|
|
MATHEMATICA
|
cf27Q[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]]==27]; Select[Range[200000], cf27Q] (* Harvey P. Dale, Mar 27 2015 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|