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A041763 Denominators of continued fraction convergents to sqrt(402). 2
1, 20, 801, 16040, 642401, 12864060, 515204801, 10316960080, 413193608001, 8274189120100, 331380758412001, 6635889357360120, 265766955052816801, 5321974990413696140, 213144766571600662401, 4268217306422426944160, 170941837023468678428801 (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 (0,802,0,-1).

FORMULA

G.f.: -(x^2-20*x-1) / (x^4-802*x^2+1). - Colin Barker, Nov 24 2013

sa(n) = 802*a(n-2) - a(n-4) for n>3. - Vincenzo Librandi, Dec 24 2013

MATHEMATICA

Denominator[Convergents[Sqrt[402], 30]] (* Vincenzo Librandi, Dec 24 2013 *)

LinearRecurrence[{0, 802, 0, -1}, {1, 20, 801, 16040}, 30] (* Harvey P. Dale, Oct 09 2017 *)

PROG

(MAGMA) I:=[1, 20, 801, 16040]; [n le 4 select I[n] else 802*Self(n-2)-Self(n-4): n in [1..40]]; // Vincenzo Librandi, Dec 24 2013

CROSSREFS

Cf. A041762, A040381.

Sequence in context: A002455 A267671 A281777 * A041760 A250550 A292417

Adjacent sequences:  A041760 A041761 A041762 * A041764 A041765 A041766

KEYWORD

nonn,frac,easy,less

AUTHOR

N. J. A. Sloane.

EXTENSIONS

a(16) from Colin Barker, Nov 24 2013

STATUS

approved

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Last modified September 22 08:23 EDT 2018. Contains 315270 sequences. (Running on oeis4.)