A031428 - OEIS

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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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

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

MATHEMATICA

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

CROSSREFS

Different from A007742.

Cf. A031424.

Sequence in context: A038346 A220243 A065007 * A007742 A225272 A276819

Adjacent sequences: A031425 A031426 A031427 * A031429 A031430 A031431

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved