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A056914 a(n) = L(4*n+1) where L() are the Lucas numbers. 7
1, 11, 76, 521, 3571, 24476, 167761, 1149851, 7881196, 54018521, 370248451, 2537720636, 17393796001, 119218851371, 817138163596, 5600748293801, 38388099893011, 263115950957276, 1803423556807921, 12360848946698171 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

REFERENCES

V. E. Hoggatt, Jr., Fibonacci and Lucas Numbers, A Publication of the Fibonacci Association, Houghton Mifflin Co., 1969, pps. 27-29.

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

Tanya Khovanova, Recursive Sequences

Index entries for linear recurrences with constant coefficients, signature (7,-1).

FORMULA

a(n) = 7*a(n-1) - a(n-2); a(0)=1, a(1)=11.

G.f.: (1+4*x)/(1-7*x+x^2). - Philippe Deléham, Nov 02 2008

EXAMPLE

a(n)={11*[((7+3*sqrt(5))/2)^n - ((7-3*sqrt(5))/2)^n]-[((7+3*sqrt(5))/2)^(n-1) - ((7-3*sqrt(5))/2)^(n-1)]}/3*sqrt(5).

MATHEMATICA

CoefficientList[Series[(1 + 4*x)/(1 - 7*x + x^2), {x, 0, 50}], x] (* or *) LinearRecurrence[{7, -1}, {1, 11}, 30] (* G. C. Greubel, Dec 24 2017 *)

PROG

(PARI) x='x+O('x^30); Vec((1+4*x)/(1-7*x+x^2)) \\ G. C. Greubel, Dec 24 2017

(MAGMA) I:=[1, 11]; [n le 2 select I[n] else 7*Self(n-1) - Self(n-2): n in [1..30]]; // G. C. Greubel, Dec 24 2017

CROSSREFS

Cf. (A056914)=sqrt{5*(A033889)^2-4}.

Cf. quadrisection of A000032: A056854 (first), this sequence (second), A246453 (third, without 11), A288913 (fourth).

Sequence in context: A034269 A256597 A245561 * A232032 A272395 A305727

Adjacent sequences:  A056911 A056912 A056913 * A056915 A056916 A056917

KEYWORD

easy,nonn

AUTHOR

Barry E. Williams, Jul 11 2000

STATUS

approved

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Last modified October 23 10:00 EDT 2018. Contains 316525 sequences. (Running on oeis4.)