A042907 Denominators of continued fraction convergents to sqrt(985).

1, 2, 3, 5, 13, 811, 1635, 2446, 4081, 10608, 661777, 1334162, 1995939, 3330101, 8656141, 540010843, 1088677827, 1628688670, 2717366497, 7063421664, 440649509665, 888362440994, 1329011950659, 2217374391653, 5763760733965, 359570539897483, 724904840528931

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, 0, 0, 0, 816, 0, 0, 0, 0, 1).

Formula

G.f.: -(x^8-2*x^7+3*x^6-5*x^5+13*x^4+5*x^3+3*x^2+2*x+1) / (x^10+816*x^5-1). - Colin Barker, Dec 25 2013

a(n) = 816*a(n-5) + a(n-10) for n>9. - Vincenzo Librandi, Feb 01 2014

Mathematica

Denominator[Convergents[Sqrt[985], 30]] (* Vincenzo Librandi, Feb 01 2014 *)
LinearRecurrence[{0, 0, 0, 0, 816, 0, 0, 0, 0, 1}, {1, 2, 3, 5, 13, 811, 1635, 2446, 4081, 10608}, 30] (* Harvey P. Dale, Jan 01 2017 *)

Prog

(Magma) I:=[1, 2, 3, 5, 13, 811, 1635, 2446, 4081, 10608]; [n le 10 select I[n] else 816*Self(n-5)+Self(n-10): n in [1..30]]; // Vincenzo Librandi, Feb 01 2014

Crossrefs

Cf. A042906, A040953.

Sequence in context: A114747 A041639 A006985 * A115347 A173654 A370850

Adjacent sequences: A042904 A042905 A042906 * A042908 A042909 A042910

Keyword

nonn,frac,easy

Author

N. J. A. Sloane.

Extensions

More terms from Colin Barker, Dec 25 2013

Status

approved