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A049682 a(n) = (L(8*n) - 2)/45, where L = A000032 (the Lucas numbers). 6
0, 1, 49, 2304, 108241, 5085025, 238887936, 11222647969, 527225566609, 24768378982656, 1163586586618225, 54663801192073921, 2568035069440856064, 120642984462528161089, 5667652234669382715121, 266259012044998459449600, 12508505913880258211416081 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

This is a divisibility sequence.

LINKS

Table of n, a(n) for n=0..16.

Index to divisibility sequences.

Index entries for linear recurrences with constant coefficients, signature (48,-48,1).

FORMULA

a(n) = (1/45)*{-2 + [(47 + 7*sqrt(45))/2]^n + [(47 - 7*sqrt(45))/2]^n}. - Ralf Stephan, Apr 14 2004

a(n)=(A004187(n))^2 = 48*a(n-1) - 48*a(n-2) + a(n-3). G.f.: -x*(1 + x)/((x - 1)*(x^2 - 47*x + 1)). [R. J. Mathar, Jun 03 2009]

a(n) = F(4n)^2/9. Also a(n) - a(n-1) = A004187(2n-1). - R. K. Guy, Feb 24 2010

From Peter Bala, Jun 03,2016: (Start)

exp( Sum_{n >= 1} 45*a(n)*x^n/n ) = 1 + 15/7*Sum_{n >= 1} Fibonacci(8*n)*x^n.

This is the particular case k = 4 of the relation exp( Sum_{n >= 1} 5*F(k*n)^2*x^n/n ) = 1 + 5*Fibonacci(k)/Lucas(k) * ( Sum_{n >= 1} F(2*k*n)*x^n ). (End)

Lim_{n->infinity} a(n+1)/a(n) = (47 + 21*sqrt(5))/2 = phi^8, where phi is the golden ratio (A001622). - Ilya Gutkovskiy, Jun 06 2016

a(n) = a(-n) for all n in Z. - Michael Somos, Jun 12 2016

0 = a(n)*(+a(n) -98*a(n+1) -2*a(n+2)) + a(n+1)*(+2401*a(n+1) -98*a(n+2)) + a(n+2)^2 for all integer n. - Michael Somos, Jun 12 2016

EXAMPLE

G.f. = x + 49*x^2 + 2304*x^3 + 108241*x^4 + 5085025*x^5 + 238887936*x^6 + ...

MATHEMATICA

LinearRecurrence[{48, -48, 1}, {0, 1, 49}, 20] (* or *) CoefficientList[Series[ (-x-x^2)/ (x^3-48x^2+48x-1), {x, 0, 20}], x] (* Harvey P. Dale, Apr 22 2011 *)

PROG

(Mupad) numlib::fibonacci(4*n)^2/9 $ n = 0..25; // Zerinvary Lajos, May 09 2008

CROSSREFS

A000045, A004146, A049683, A049684.

Sequence in context: A163927 A245036 A061615 * A162914 A163287 A163835

Adjacent sequences:  A049679 A049680 A049681 * A049683 A049684 A049685

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling

EXTENSIONS

More terms from N. J. A. Sloane, Feb 26 2010

STATUS

approved

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Last modified June 22 08:08 EDT 2017. Contains 288605 sequences.