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A090251 a(n) =29a(n-1) - a(n-2), starting with a(0) = 2 and a(1) = 29. +0
2
2, 29, 839, 24302, 703919, 20389349, 590587202, 17106639509, 495501958559, 14352450158702, 415725552643799, 12041688576511469, 348793243166188802, 10102962363242963789, 292637115290879761079, 8476373381072270107502 (list; graph; listen)
OFFSET

0,1

COMMENT

a(n+1)/a(n) converges to ((29+sqrt(837))/2) =28.9654761... Lim a(n)/a(n+1) as n approaches infinity = 0.0345238... =2/(29+sqrt(837)) =(29-sqrt(837))/2. Lim a(n+1)/a(n) as n approaches infinity = 28.9654761... = (29+sqrt(837))/2=2/(29-sqrt(837)). Lim a(n)/a(n+1) = 29 - Lim a(n+1)/a(n).

A Chebyshev T-sequence with a Diophantine property.

a(n) gives the general (nonnegative integer) solution of the Pell equation a^2 - 93*(3*b)^2 =+4 with companion sequence b(n)=A097782(n+1), n>=0.

REFERENCES

O. Perron, "Die Lehre von den Kettenbruechen, Bd.I", Teubner, 1954, 1957 (Sec. 30, Satz 3.35, p. 109 and table p. 108).

LINKS

Tanya Khovanova, Recursive Sequences

Index entries for recurrences a(n) = k*a(n - 1) +/- a(n - 2)

Index entries for sequences related to Chebyshev polynomials.

FORMULA

a(n) =29a(n-1) - a(n-2), starting with a(0) = 2 and a(1) = 29. a(n) = ((29+sqrt(837))/2)^n + ((29-sqrt(837))/2)^n, (a(n))^2 =a(2n)+2.

a(n) = S(n, 29) - S(n-2, 29) = 2*T(n, 29/2) with S(n, x) := U(n, x/2), S(-1, x) := 0, S(-2, x) := -1. S(n, 27)=A097781(n). U-, resp. T-, are Chebyshev's polynomials of the second, resp. first, kind. See A049310 and A053120.

a(n) = ap^n + am^n, with ap := (29+3*sqrt(93))/2 and am := (29-3*sqrt(93))/2.

G.f.: (2-29*x)/(1-29*x+x^2).

EXAMPLE

a(4) =703919 = 29a(3) - a(2) = 29*24302 - 839= ((29+sqrt(837))/2)^4 + ((29-sqrt(837))/2)^4 = 703918.99999857 + 0.00000142 =703919.

(x,y) = (2;0), (29;1), (839;29), (24302,840), ..., give the

nonnegative integer solutions to x^2 - 93*(3*y)^2 =+4.

MATHEMATICA

a[0] = 2; a[1] = 29; a[n_] := 29a[n - 1] - a[n - 2]; Table[ a[n], {n, 0, 15}] (from Robert G. Wilson v Jan 30 2004)

PROGRAM

sage: [lucas_number2(n, 29, 1) for n in xrange(0, 16)] - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 27 2008

CROSSREFS

Cf. A083148, A007610.

a(n)=sqrt(4 + 93*(3*A097782(n-1))^2), n>=1.

Cf. A077428, A078355 (Pell +4 equations).

Cf. A090248 for 2*T(n, 27/2).

Sequence in context: A104535 A013517 A006988 this_sequence A087281 A024234 A077282

Adjacent sequences: A090248 A090249 A090250 this_sequence A090252 A090253 A090254

KEYWORD

easy,nonn

AUTHOR

Nikolay V. Kosinov (kosinov(AT)unitron.com.ua), Jan 24 2004

EXTENSIONS

More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 30 2004

Chebyshev and Pell comments from W. Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de), Aug 31 2004

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Last modified December 7 23:50 EST 2009. Contains 170430 sequences.


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