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A041775 Denominators of continued fraction convergents to sqrt(408). 2
1, 5, 201, 1010, 40601, 204015, 8201201, 41210020, 1656602001, 8324220025, 334625403001, 1681451235030, 67592674804201, 339644825256035, 13653385685045601, 68606573250484040, 2757916315704407201, 13858188151772520045, 557085442386605209001 (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 (0,202,0,-1).

FORMULA

G.f.: -(x^2-5*x-1) / (x^4-202*x^2+1). - Colin Barker, Nov 24 2013

a(n) = 202*a(n-2) - a(n-4). for n>3. - Vincenzo Librandi, Dec 24 2013

MATHEMATICA

Denominator[Convergents[Sqrt[408], 30]] (* Vincenzo Librandi, Dec 24 2013 *)

PROG

(MAGMA) I:=[1, 5, 201, 1010]; [n le 4 select I[n] else 202*Self(n-2)-Self(n-4): n in [1..40]]; // Vincenzo Librandi, Dec 24 2013

CROSSREFS

Cf. A041774, A040387.

Sequence in context: A128791 A303136 A244848 * A093976 A337579 A196799

Adjacent sequences:  A041772 A041773 A041774 * A041776 A041777 A041778

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 January 20 04:53 EST 2021. Contains 340301 sequences. (Running on oeis4.)