%I #20 Sep 08 2022 08:44:55
%S 1,1,3,13,29,42,2129,2171,6471,28055,62581,90636,4594381,4685017,
%T 13964415,60542677,135049769,195592446,9914672069,10110264515,
%U 30135201099,130651068911,291437338921,422088407832,21395857730521,21817946138353,65031750007227
%N Denominators of continued fraction convergents to sqrt(660).
%H Vincenzo Librandi, <a href="/A042269/b042269.txt">Table of n, a(n) for n = 0..200</a>
%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,2158,0,0,0,0,0,-1).
%F G.f.: -(x^10 -x^9 +3*x^8 -13*x^7 +29*x^6 -42*x^5 -29*x^4 -13*x^3 -3*x^2 -x -1) / ((x^4 -13*x^2 +1)*(x^8 +13*x^6 +168*x^4 +13*x^2 +1)). - _Colin Barker_, Dec 06 2013
%F a(n) = 2158*a(n-6) - a(n-12) for n>11. - _Vincenzo Librandi_, Jan 19 2014
%p convert(sqrt(660),confrac,30,cvgts): denom(cvgts); # _Wesley Ivan Hurt_, Dec 07 2013
%t Denominator/@Convergents[Sqrt[660], 30] (* _Harvey P. Dale_, Jul 15 2011 *)
%o (Magma) I:=[1,1,3,13,29,42,2129,2171,6471,28055,62581, 90636]; [n le 12 select I[n] else 2158*Self(n-6)-Self(n-12): n in [1..40]]; // _Vincenzo Librandi_, Jan 19 2014
%Y Cf. A042268, A040634.
%K nonn,frac,easy
%O 0,3
%A _N. J. A. Sloane_.
%E More terms from _Colin Barker_, Dec 06 2013