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A007655 Standard deviation of A007654.
(Formerly M4948)
+0
20
0, 1, 14, 195, 2716, 37829, 526890, 7338631, 102213944, 1423656585, 19828978246, 276182038859, 3846719565780, 53577891882061, 746243766783074, 10393834843080975, 144767444036350576 (list; graph; listen)
OFFSET

1,3

COMMENT

a(n)=A001353(2n)/4. a(n) corresponds also to one-sixth the area of Fleenor-Heronian triangle with middle side A003500(n). - Lekraj Beedassy (blekraj(AT)yahoo.com), Jul 15 2002

a(n) give all (nontrivial, integer) solutions of Pell equation b(n+1)^2 - 48*a(n+1)^2 = +1 with b(n+1)=A011943(n), n>=0.

REFERENCES

D. A. Benaron, personal communication.

E. K. Lloyd (E.K.Lloyd(AT)maths.soton.ac.uk), "The standard deviation of 1, 2, .., n, Pell's equation and rational triangles", preprint.

LINKS

T. D. Noe, Table of n, a(n) for n=1..100

Tanya Khovanova, Recursive Sequences

Index entries for sequences related to Chebyshev polynomials.

Zerinvary Lajos, Sage Notebooks

FORMULA

a(n) = 14*a(n-1) - a(n-2). G.f.: (x^2)/(1-14*x+x^2).

a(n+1) ~ 1/24*sqrt(3)*(2 + sqrt(3))^(2*n) - Joe Keane (jgk(AT)jgk.org), May 15 2002

a(n+1) = S(n-1, 14), n>=0, with S(n, x) := U(n, x/2) Chebyshev's polynomials of the second kind. S(-1, x) := 0. See A049310.

a(n+1) = ((7+4*sqrt(3))^n - (7-4*sqrt(3))^n)/(8*sqrt(3)).

a(n+1) = sqrt((A011943(n)^2 - 1)/48), n>=0.

Chebyshev's polynomials U(n-2, x) evaluated at x=7.

4*a(n+1) + A046184(n) = A055793(n+2) + A098301(n+1) 4*a(n+1) + A098301(n+1) + A055793(n+2) = A046184(n+1) (4*a(n+1))^2 = A098301(2n+1) (conjectures) - Creighton Dement (creighton.k.dement(AT)uni-oldenburg.de), Nov 02 2004

(4*a(n))^2 = A103974(n)^2 - A011922(n-1)^2. - Paul D. Hanna (pauldhanna(AT)juno.com), Mar 06 2005

a(n) = 13*(a(n-1)+a(n-2))-a(n-3), a(n) = 15*(a(n-1)-a(n-2))+a(n-3). a(n)=14*a(n-1)-a(n-2). - Mohamed Bouhamida (bhmd95(AT)yahoo.fr), May 26 2007

PROGRAM

sage: [lucas_number1(n, 14, 1) for n in xrange(0, 20)] - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 25 2008

CROSSREFS

Cf. A001353, A003500.

Cf. A011945, A067900.

Cf. A103974, A011922.

Sequence in context: A091030 A055759 A086946 this_sequence A001023 A067221 A072533

Adjacent sequences: A007652 A007653 A007654 this_sequence A007656 A007657 A007658

KEYWORD

nonn,easy

AUTHOR

njas

EXTENSIONS

Chebyshev comments from W. Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de), Nov 08 2002

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Last modified July 19 08:04 EDT 2008. Contains 142098 sequences.


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