A042239 Denominators of continued fraction convergents to sqrt(645).

1, 2, 3, 5, 63, 635, 7683, 8318, 16001, 40320, 2032001, 4104322, 6136323, 10240645, 129024063, 1300481275, 15734799363, 17035280638, 32770080001, 82575440640, 4161542112001, 8405659664642, 12567201776643, 20972861441285, 264241539072063, 2663388252161915

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, 0, 0, 0, 0, 0, 0, 0, 0, 2048002, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1).

Formula

G.f.: -(x^18 - 2*x^17 + 3*x^16 - 5*x^15 + 63*x^14 - 635*x^13 + 7683*x^12 - 8318*x^11 + 16001*x^10 - 40320*x^9 - 16001*x^8 - 8318*x^7 - 7683*x^6 - 635*x^5 - 63*x^4 - 5*x^3 - 3*x^2 - 2*x - 1) / (x^20 - 2048002*x^10 + 1). - Colin Barker, Dec 05 2013

Mathematica

Denominator[Convergents[Sqrt[645], 30]] (* Vincenzo Librandi, Jan 18 2014 *)

Crossrefs

Cf. A042238, A040619.

Sequence in context: A084839 A259382 A103110 * A270582 A270916 A381224

Adjacent sequences: A042236 A042237 A042238 * A042240 A042241 A042242

Keyword

nonn,frac,easy

Author

N. J. A. Sloane

Extensions

More terms from Colin Barker, Dec 05 2013

Status

approved