A041391 Denominators of continued fraction convergents to sqrt(210).

1, 2, 57, 116, 3305, 6726, 191633, 389992, 11111409, 22612810, 644270089, 1311152988, 37356553753, 76024260494, 2166035847585, 4408095955664, 125592722606177, 255593541168018, 7282211875310681, 14820017291789380, 422242696045413321

Offset

0,2

Links

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

Index entries for linear recurrences with constant coefficients, signature (0,58,0,-1).

Formula

G.f.: -(x^2-2*x-1) / (x^4-58*x^2+1). - Colin Barker, Nov 17 2013

a(n) = 58*a(n-2) - a(n-4) for n>3. - Vincenzo Librandi, Dec 17 2013

Mathematica

Denominator[Convergents[Sqrt[210], 30]] (* Vincenzo Librandi, Dec 17 2013 *)

Prog

(Magma) I:=[1, 2, 57, 116]; [n le 4 select I[n] else 58*Self(n-2)-Self(n-4): n in [1..40]]; // Vincenzo Librandi, Dec 17 2013

Crossrefs

Cf. A041390, A176441, A040195.

Sequence in context: A002542 A264939 A201217 * A245783 A189057 A229015

Adjacent sequences: A041388 A041389 A041390 * A041392 A041393 A041394

Keyword

nonn,frac,easy

Author

N. J. A. Sloane.

Extensions

More terms from Colin Barker, Nov 17 2013

Status

approved