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A041769

Denominators of continued fraction convergents to sqrt(405).

1, 8, 321, 2576, 103361, 829464, 33281921, 267084832, 10716675201, 86000486440, 3450736132801, 27691889548848, 1111126318086721, 8916702434242616, 357779223687791361, 2871150491936573504, 115203798901150731521, 924501541701142425672

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OFFSET

0,2

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (0,322,0,-1).

FORMULA

G.f.: -(x^2-8*x-1) / ((x^2-18*x+1)*(x^2+18*x+1)). - Colin Barker, Nov 24 2013

a(n) = 322*a(n-2) - a(n-4) for n>3. - Vincenzo Librandi, Dec 24 2013

MATHEMATICA

Denominator[Convergents[Sqrt[405], 30]] (* Vincenzo Librandi, Dec 24 2013 *)

PROG

(Magma) I:=[1, 8, 321, 2576]; [n le 4 select I[n] else 322*Self(n-2)-Self(n-4): n in [1..40]]; // Vincenzo Librandi, Dec 24 2013

CROSSREFS

Cf. A041768, A040384.

Sequence in context: A227657 A057982 A308615 * A209277 A182275 A171248

Adjacent sequences: A041766 A041767 A041768 * A041770 A041771 A041772

KEYWORD

nonn,frac,easy

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Colin Barker, Nov 24 2013

STATUS

approved

URL: https://oeis.org/A041769

⇱ A041769 - OEIS