A041779 Denominators of continued fraction convergents to sqrt(410).

1, 4, 161, 648, 26081, 104972, 4224961, 17004816, 684417601, 2754675220, 110871426401, 446240380824, 17960486659361, 72288187018268, 2909487967390081, 11710240056578592, 471319090230533761, 1896986600978713636, 76350783129379079201

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, 162, 0, -1).

Formula

a(n) = 162*a(n-2)-a(n-4). G.f.: -(x^2-4*x-1)/(x^4-162*x^2+1). [Colin Barker, Jul 16 2012]

Mathematica

Denominator[Convergents[Sqrt[410], 30]] (* Harvey P. Dale, Nov 06 2011 *)
CoefficientList[Series[(1 + 4 x - x^2)/(x^4 - 162 x^2 + 1), {x, 0, 30}], x] (* Vincenzo Librandi, Dec 24 2013 *)

Prog

(Magma) I:=[1, 4, 161, 648]; [n le 4 select I[n] else 162*Self(n-2)-Self(n-4): n in [1..40]]; // Vincenzo Librandi, Dec 24 2013

Crossrefs

Cf. A041778.

Sequence in context: A214007 A248330 A157463 * A222394 A306350 A125532

Adjacent sequences: A041776 A041777 A041778 * A041780 A041781 A041782

Keyword

nonn,frac,easy

Author

N. J. A. Sloane.

Extensions

More terms from Vincenzo Librandi, Dec 24 2013

Status

approved