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A041387 Denominators of continued fraction convergents to sqrt(208). 2
1, 2, 5, 7, 19, 45, 1279, 2603, 6485, 9088, 24661, 58410, 1660141, 3378692, 8417525, 11796217, 32009959, 75816135, 2154861739, 4385539613, 10925940965, 15311480578, 41548902121, 98409284820, 2797008877081, 5692427038982, 14181862955045, 19874289994027 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,1298,0,0,0,0,0,-1).

FORMULA

G.f.: -(x^4 -2*x^3 +5*x^2 +2*x +1)*(x^6 -9*x^3 -1) / ((x^2 -3*x -1)*(x^2 +3*x -1)*(x^4 -3*x^3 +10*x^2 +3*x +1)*(x^4 +3*x^3 +10*x^2 -3*x +1)). - Colin Barker, Nov 16 2013

a(n) = 1298*a(n-6) - a(n-12) for n>11. - Vincenzo Librandi, Dec 17 2013

MATHEMATICA

Denominator[Convergents[Sqrt[208], 30]] (* Vincenzo Librandi, Dec 17 2013 *)

PROG

(MAGMA) I:=[1, 2, 5, 7, 19, 45, 1279, 2603, 6485, 9088, 24661, 58410]; [n le 12 select I[n] else 1298*Self(n-6)-Self(n-12): n in [1..40]]; // Vincenzo Librandi, Dec 17 2013

CROSSREFS

Cf. A041386, A040193.

Sequence in context: A215212 A106872 A071198 * A096146 A041583 A143915

Adjacent sequences:  A041384 A041385 A041386 * A041388 A041389 A041390

KEYWORD

nonn,frac,easy

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Colin Barker, Nov 16 2013

STATUS

approved

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Last modified December 8 14:41 EST 2021. Contains 349596 sequences. (Running on oeis4.)