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A041761 Denominators of continued fraction convergents to sqrt(401). 2
1, 40, 1601, 64080, 2564801, 102656120, 4108809601, 164455040160, 6582310416001, 263456871680200, 10544857177624001, 422057743976640240, 16892854616243233601, 676136242393705984280, 27062342550364482604801, 1083169838256973010176320 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

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

Tanya Khovanova, Recursive Sequences

Index entries for linear recurrences with constant coefficients, signature (40,1).

FORMULA

a(n) = F(n, 40), the n-th Fibonacci polynomial evaluated at x=40. - T. D. Noe, Jan 19 2006

From Philippe Deléham, Nov 23 2008: (Start)

a(n) = 40*a(n-1) + a(n-2), n>1; a(0)=1, a(1)=40.

G.f.: 1/(1 - 40*x - x^2). (End)

MATHEMATICA

a=0; lst={}; s=0; Do[a=s-(a-1); AppendTo[lst, a]; s+=a*40, {n, 3*4!}]; lst (* Vladimir Joseph Stephan Orlovsky, Nov 03 2009 *)

Denominator[Convergents[Sqrt[401], 20]] (* Harvey P. Dale, Aug 18 2012 *)

CoefficientList[Series[1/(1 - 40 x - x^2), {x, 0, 30}], x] (* Vincenzo Librandi, Dec 24 2013 *)

CROSSREFS

Cf. A041760, A040380.

Sequence in context: A207740 A208082 A009984 * A229635 A278431 A229584

Adjacent sequences:  A041758 A041759 A041760 * A041762 A041763 A041764

KEYWORD

nonn,frac,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified June 29 08:41 EDT 2017. Contains 288859 sequences.