A041757 Denominators of continued fraction convergents to sqrt(398).

1, 1, 19, 20, 779, 799, 15161, 15960, 621641, 637601, 12098459, 12736060, 496068739, 508804799, 9654555121, 10163359920, 395862232081, 406025592001, 7704322888099, 8110348480100, 315897565131899, 324007913611999, 6148040010147881, 6472047923759880

Offset

0,3

Links

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

Index entries for linear recurrences with constant coefficients, signature (0,0,0,798,0,0,0,-1).

Formula

G.f.: -(x^2-x-1)*(x^4+20*x^2+1) / (x^8-798*x^4+1). - Colin Barker, Nov 24 2013

a(n) = 798*a(n-4) - a(n-8) for n>7. - Vincenzo Librandi, Dec 24 2013

Mathematica

Denominator[Convergents[Sqrt[398], 30]] (* Vincenzo Librandi, Dec 24 2013 *)

Prog

(Magma) I:=[1, 1, 19, 20, 779, 799, 15161, 15960]; [n le 8 select I[n] else 798*Self(n-4)-Self(n-8): n in [1..40]]; // Vincenzo Librandi, Dec 24 2013

Crossrefs

Cf. A041756, A040378.

Sequence in context: A197353 A041179 A041756 * A041758 A042735 A156758

Adjacent sequences: A041754 A041755 A041756 * A041758 A041759 A041760

Keyword

nonn,frac,easy

Author

N. J. A. Sloane.

Extensions

More terms from Colin Barker, Nov 24 2013

Status

approved