A041763 Denominators of continued fraction convergents to sqrt(402).

1, 20, 801, 16040, 642401, 12864060, 515204801, 10316960080, 413193608001, 8274189120100, 331380758412001, 6635889357360120, 265766955052816801, 5321974990413696140, 213144766571600662401, 4268217306422426944160, 170941837023468678428801

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

a(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: A322890 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