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A041767 Denominators of continued fraction convergents to sqrt(404). 2
1, 10, 401, 4020, 161201, 1616030, 64802401, 649640040, 26050404001, 261153680050, 10472197606001, 104983129740060, 4209797387208401, 42202957001824070, 1692328077460171201, 16965483731603536080, 680311677341601614401, 6820082257147619680090 (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 (0,402,0,-1).

FORMULA

G.f.: -(x^2-10*x-1) / ((x^2-20*x-1)*(x^2+20*x-1)). - Colin Barker, Nov 24 2013

a(n) = 402*a(n-2) - a(n-4) for n>3. - Vincenzo Librandi, Dec 24 2013

MATHEMATICA

Denominator[Convergents[Sqrt[404], 30]] (* Vincenzo Librandi, Dec 24 2013 *)

PROG

(MAGMA) I:=[1, 10, 401, 4020]; [n le 4 select I[n] else 402*Self(n-2)-Self(n-4): n in [1..40]]; // Vincenzo Librandi, Dec 24 2013

CROSSREFS

Cf. A041766, A040383.

Sequence in context: A172505 A098722 A162677 * A130557 A231052 A085000

Adjacent sequences:  A041764 A041765 A041766 * A041768 A041769 A041770

KEYWORD

nonn,frac,easy

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Colin Barker, Nov 24 2013

STATUS

approved

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Last modified September 29 12:15 EDT 2020. Contains 337431 sequences. (Running on oeis4.)