A041775 Denominators of continued fraction convergents to sqrt(408).

1, 5, 201, 1010, 40601, 204015, 8201201, 41210020, 1656602001, 8324220025, 334625403001, 1681451235030, 67592674804201, 339644825256035, 13653385685045601, 68606573250484040, 2757916315704407201, 13858188151772520045, 557085442386605209001

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