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A041721
Denominators of continued fraction convergents to sqrt(380).
2
1, 2, 77, 156, 6005, 12166, 468313, 948792, 36522409, 73993610, 2848279589, 5770552788, 222129285533, 450029123854, 17323235991985, 35096501107824, 1350990278089297, 2737077057286418, 105359918454973181, 213456913967232780, 8216722649209818821
OFFSET
0,2
FORMULA
G.f.: -(x^2-2*x-1) / (x^4-78*x^2+1). - Colin Barker, Nov 22 2013
a(n) = 78*a(n-2) - a(n-4) for n>3. - Vincenzo Librandi, Dec 23 2013
MAPLE
convert(sqrt(380), confrac, 30, cvgts): denom(cvgts); # Wesley Ivan Hurt, Dec 23 2013
MATHEMATICA
Denominator[Convergents[Sqrt[380], 30]] (* Harvey P. Dale, May 29 2013 *)
CoefficientList[Series[(1 + 2 x - x^2)/(x^4 - 78 x^2 + 1), {x, 0, 30}], x] (* Vincenzo Librandi, Dec 23 2013 *)
PROG
(Magma) I:=[1, 2, 77, 156]; [n le 4 select I[n] else 78*Self(n-2)-Self(n-4): n in [1..40]]; // Vincenzo Librandi, Dec 23 2013
CROSSREFS
Sequence in context: A349066 A266877 A301472 * A048358 A124456 A338588
KEYWORD
nonn,frac,easy
AUTHOR
EXTENSIONS
More terms from Colin Barker, Nov 22 2013
STATUS
approved