A042897 Denominators of continued fraction convergents to sqrt(980).

1, 3, 10, 13, 23, 59, 82, 141, 505, 1656, 103177, 311187, 1036738, 1347925, 2384663, 6117251, 8501914, 14619165, 52359409, 171697392, 10697597713, 32264490531, 107491069306, 139755559837, 247246629143, 634248818123, 881495447266, 1515744265389, 5428728243433

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, 103682, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1).

Formula

G.f.: -(x^18 - 3*x^17 + 10*x^16 - 13*x^15 + 23*x^14 - 59*x^13 + 82*x^12 - 141*x^11 + 505*x^10 - 1656*x^9 - 505*x^8 - 141*x^7 - 82*x^6 - 59*x^5 - 23*x^4 - 13*x^3 - 10*x^2 - 3*x - 1) / ((x^10 - 322*x^5 + 1)*(x^10 + 322*x^5 + 1)). - Colin Barker, Dec 25 2013

a(n) = 103682*a(n-10) - a(n-20) for n > 19. - Vincenzo Librandi, Feb 01 2014

Mathematica

Denominator[Convergents[Sqrt[980], 30]] (* Harvey P. Dale, Jul 23 2012 *)

Crossrefs

Cf. A042896, A040948.

Sequence in context: A235089 A022122 A042479 * A041169 A068361 A285181

Adjacent sequences: A042894 A042895 A042896 * A042898 A042899 A042900

Keyword

nonn,frac,easy

Author

N. J. A. Sloane

Extensions

More terms from Colin Barker, Dec 25 2013

Status

approved