A042921 Denominators of continued fraction convergents to sqrt(992).

1, 2, 125, 252, 15749, 31750, 1984249, 4000248, 249999625, 503999498, 31497968501, 63499936500, 3968494031501, 8000487999502, 499998750000625, 1007997988000752, 62995874006047249, 126999746000095250, 7936980126011952749, 16000959998024000748

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..200

Index entries for linear recurrences with constant coefficients, signature (0, 126, 0, -1).

Formula

G.f.: -(x^2-2*x-1) / (x^4-126*x^2+1). - Colin Barker, Dec 25 2013

a(n) = 126*a(n-2) - a(n-4) for n>3. - Vincenzo Librandi, Feb 01 2014

Mathematica

Denominator[Convergents[Sqrt[992], 30]] (* Vincenzo Librandi, Feb 01 2014 *)

Prog

(Magma) I:=[1, 2, 125, 252]; [n le 4 select I[n] else 126*Self(n-2)-Self(n-4): n in [1..30]]; // Vincenzo Librandi, Feb 01 2014

Crossrefs

Cf. A042920, A040960.

Sequence in context: A065705 A012870 A183720 * A123006 A028481 A049659

Adjacent sequences: A042918 A042919 A042920 * A042922 A042923 A042924

Keyword

nonn,frac,easy

Author

N. J. A. Sloane

Extensions

More terms from Colin Barker, Dec 25 2013

Status

approved