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A042219 Denominators of continued fraction convergents to sqrt(635). 2
1, 5, 251, 1260, 63251, 317515, 15939001, 80012520, 4016565001, 20162837525, 1012158441251, 5080955043780, 255059910630251, 1280380508195035, 64274085320382001, 322650807110105040, 16196814440825634001, 81306723011238275045, 4081532965002739386251 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

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

Index to sequences with linear recurrences with constant coefficients, signature (0,252,0,-1).

FORMULA

G.f.: -(x^2-5*x-1) / (x^4-252*x^2+1). - Colin Barker, Dec 04 2013

a(n) = 252*a(n-2) - a(n-4) for n>3. - Vincenzo Librandi, Jan 17 2014

MATHEMATICA

Denominator[Convergents[Sqrt[635], 30]] (* Vincenzo Librandi, Jan 17 2014_ *)

PROG

(MAGMA) I:=[1, 5, 251, 1260]; [n le 4 select I[n] else 252*Self(n-2)-Self(n-4): n in [1..30]]; // Vincenzo Librandi, Jan 17 2014

CROSSREFS

Cf. A042218, A040609.

Sequence in context: A219872 A115739 A142202 * A198600 A213446 A060943

Adjacent sequences:  A042216 A042217 A042218 * A042220 A042221 A042222

KEYWORD

nonn,frac,easy

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Colin Barker, Dec 04 2013

STATUS

approved

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Last modified November 25 18:10 EST 2014. Contains 250000 sequences.