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A247565 a(n) = 5*a(n-1) - 10*a(n-2) + 8*a(n-3) with a(0) = 2, a(1) = a(2) = 3. 2
2, 3, 3, 1, -1, 9, 63, 217, 527, 969, 1311, 1081, 47, -87, 7743, 39961, 121679, 270729, 456543, 548857, 344687, -112791, 380031, 5785561, 24225167, 66310473, 135585183, 208622521, 217744559, 87179049, -72570177, 507315097, 3959709647, 14144835849, 35185603551 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..2500

Index entries for linear recurrences with constant coefficients, signature (5,-10,8).

FORMULA

G.f.: (2 - 7*x + 8*x^2) / (1 - 5*x + 10*x^2 - 8*x^3).

(n) = a(-1-n) * 2^(2*n+1) for all n in Z.

a(n) = 2^n + A247560(n) for all n in Z.

a(n) = A247564(n+1) * A247564(n) for all n in Z.

0 = a(n)*(+4*a(n+1) + 2*a(n+2)) + a(n+1)*(-5*a(n+1) + a(n+2)) for all n in Z.

a(n) = 2^n + (1/2)*((3/2 + (1/2)*i*sqrt(7))^n + (3/2 - (1/2)*i*sqrt(7))^n) + (1/14)*i*sqrt(7)*((3/2 + (1/2)*i*sqrt(7))^n - (3/2 - (1/2)*i*sqrt(7))^n). - Paolo P. Lava, Sep 22 2014

EXAMPLE

G.f. = 2 + 3*x + 3*x^2 + x^3 - x^4 + 9*x^5 + 63*x^6 + 217*x^7 + 527*x^8 + ...

MATHEMATICA

CoefficientList[Series[(2-7*x+8*x^2)/(1-5*x+10*x^2-8*x^3), {x, 0, 60}], x] (* or *) LinearRecurrence[{5, -10, 8}, {2, 3, 3}, 60] (* G. C. Greubel, Aug 04 2018 *)

PROG

(PARI) {a(n) = 2^n + real( (1 + quadgen(-7))^n )};

(PARI) Vec((2 - 7*x + 8*x^2) / (1 - 5*x + 10*x^2 - 8*x^3) + O(x^50)) \\ Michel Marcus, Sep 22 2014

(Magma) m:=60; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!((2-7*x+8*x^2)/(1-5*x+10*x^2-8*x^3))); // G. C. Greubel, Aug 04 2018

CROSSREFS

Cf. A247560, A247564.

Sequence in context: A209007 A145854 A097663 * A204259 A066517 A108132

Adjacent sequences: A247562 A247563 A247564 * A247566 A247567 A247568

KEYWORD

sign,easy

AUTHOR

Michael Somos, Sep 20 2014

STATUS

approved

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Last modified November 30 18:07 EST 2022. Contains 358453 sequences. (Running on oeis4.)