A031768 Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 90.

2026, 8102, 18228, 32404, 50630, 72906, 99232, 129608, 164034, 202510, 245036, 291612, 342238, 396914, 455640, 518416, 585242, 656118, 731044, 810020, 893046, 980122, 1071248, 1166424, 1265650, 1368926, 1476252, 1587628, 1703054, 1822530

Offset

1,1

Comments

A156856 is almost certainly a proper sequence of this sequence. - Franklin T. Adams-Watters, Feb 21 2009

In fact the first term not of the form A156856(n)=(45n)^2+n is a(93) = 17147972, with contfrac(sqrt(17147972)) = [4141; [91, 90, 91, 8282]]. - M. F. Hasler, Feb 21 2009

The first term not of the form A156856(n)=(45n)^2+n is a(93) = 17147972, with contfrac(sqrt(17147972)) = [4141; [91, 90, 91, 8282]]. - M. F. Hasler, Feb 21 2009

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Mathematica

cf90Q[n_]:=With[{s=Sqrt[n]}, If[IntegerQ[s], 1, Min[ContinuedFraction[s][[2]]]]==90]; Select[Range[1823000], cf90Q] (* Harvey P. Dale, Jan 20 2025 *)

Crossrefs

Cf. A156856.

Sequence in context: A360216 A250811 A350869 * A156856 A031543 A031723

Adjacent sequences: A031765 A031766 A031767 * A031769 A031770 A031771

Keyword

nonn

Author

David W. Wilson

Status

approved