A031512 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 14.

198, 206, 214, 238, 242, 246, 254, 444, 453, 471, 489, 501, 507, 516, 537, 543, 573, 788, 796, 844, 860, 876, 892, 908, 916, 924, 932, 940, 956, 964, 972, 988, 1004, 1020, 1230, 1245, 1255, 1270, 1345, 1355, 1405, 1420, 1470, 1505, 1545, 1555, 1595, 1770, 1866

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Mathematica

cf14Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {1}, ContinuedFraction[s][[2]]]; len=Length[cf]; EvenQ[len]&&cf[[len/2]]==14]; Select[Range[2000], cf14Q] (* Harvey P. Dale, Apr 04 2013 *)

Crossrefs

Sequence in context: A145452 A286853 A025375 * A260193 A025366 A248534

Adjacent sequences: A031509 A031510 A031511 * A031513 A031514 A031515

Keyword

nonn

Author

David W. Wilson

Status

approved