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A041720 Numerators of continued fraction convergents to sqrt(380). 2
19, 39, 1501, 3041, 117059, 237159, 9129101, 18495361, 711952819, 1442400999, 55523190781, 112488782561, 4330096928099, 8772682638759, 337692037200941, 684156757040641, 26335648804745299, 53355454366531239 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (0, 78, 0, -1).

FORMULA

G.f.: (19+39*x+19*x^2-x^3)/(1-78*x^2+x^4). - Vincenzo Librandi, Mov 07 2013

a(n) = 78*a(n-2)-a(n-4). - Vincenzo Librandi, Nov 07 2013

MATHEMATICA

Numerator[Convergents[Sqrt[380], 30]] (* or *) CoefficientList[Series[(19 + 39 x + 19 x^2 - x^3)/(1 - 78 x^2 + x^4), {x, 0, 30}], x] (* Vincenzo Librandi, Nov 07 2013 *)

PROG

(MAGMA) I:=[19, 39, 1501, 3041]; [n le 4 select I[n] else 78*Self(n-2)-Self(n-4): n in [1..30]]; // Vincenzo Librandi, Nov 07 2013

CROSSREFS

Cf. A041721.

Sequence in context: A041714 A041716 A041718 * A098850 A264537 A164078

Adjacent sequences:  A041717 A041718 A041719 * A041721 A041722 A041723

KEYWORD

nonn,cofr,frac,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified September 17 12:00 EDT 2021. Contains 347477 sequences. (Running on oeis4.)