A031428 Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 4.

5, 18, 39, 68, 105, 150, 174, 203, 264, 333, 370, 410, 495, 588, 689, 793, 798, 855, 915, 1040, 1105, 1173, 1313, 1314, 1378, 1387, 1462, 1463, 1620, 1785, 1958, 2138, 2139, 2222, 2232, 2328, 2525, 2730, 2834, 2943, 3164, 3393, 3630, 3741

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 (first 700 terms from Vincenzo Librandi)

Crossrefs

Different from A007742.

Cf. A031424.

Programs

Mathematica

Select[Range[4000], !IntegerQ[Sqrt[#]] && Min[ContinuedFraction[Sqrt[#]][[2]]] == 4&] (* Vincenzo Librandi, Feb 06 2012 *)