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A041838 Numerators of continued fraction convergents to sqrt(440). 2
20, 21, 860, 881, 36100, 36981, 1515340, 1552321, 63608180, 65160501, 2670028220, 2735188721, 112077577060, 114812765781, 4704588208300, 4819400974081, 197480627171540, 202300028145621, 8289481752996380 (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 (0,42,0,-1).

FORMULA

G.f.: (20 + 21*x + 20*x^2 - x^3)/(1 - 42*x^2 + x^4). - Vincenzo Librandi, Nov 10 2013

a(n) = 42*a(n-2) - a(n-4). - Vincenzo Librandi, Nov 10 2013

MATHEMATICA

Numerator[Convergents[Sqrt[440], 30]] (* or *) CoefficientList[Series[(20 + 21 x + 20 x^2 - x^3)/(1 - 42 x^2 + x^4), {x, 0, 25}], x] (* Vincenzo Librandi, Nov 10 2013 *)

PROG

(MAGMA) I:=[20, 21, 860, 881]; [n le 8 select I[n] else 42*Self(n-2)-Self(n-4): n in [1..25]]; // Vincenzo Librandi, Nov 10 2013

CROSSREFS

Cf. A041839.

Sequence in context: A302205 A041836 A041837 * A128356 A109212 A259742

Adjacent sequences:  A041835 A041836 A041837 * A041839 A041840 A041841

KEYWORD

nonn,cofr,frac,easy,less

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified November 12 19:33 EST 2019. Contains 329078 sequences. (Running on oeis4.)