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A089181 (1,3) entry of powers of the orthogonal design shown in A090592. 4
1, 2, -3, -20, -19, 102, 337, -40, -2439, -4598, 7877, 47940, 40741, -254098, -793383, 191920, 5937521, 10531602, -20499443, -114720100, -85944099, 631152502, 1863913697, -690240120, -14427876119, -24024071398, 52946990037, 274062479860, 177496029461 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (2, -7).

FORMULA

a(n) = 2*a(n-1) - 7*a(n-2); a(1)=1, a(2)=2. - T. D. Noe, Dec 11 2006

a(n) = (1/2)*(1+i*sqrt(6))^(n-1) + (1/2)*(1-i*sqrt(6))^(n-1) + (1/12)*i*(1-i*sqrt(6))^(n-1)*sqrt(6) - (1/12)*i*(1+i*sqrt(6))^(n-1)*sqrt(6) for n >= 0, where i=sqrt(-1). - Paolo P. Lava, Jun 10 2008

G.f.: x/(1 - 2*x + 7*x^2). - Philippe Deléham, Mar 04 2012

MATHEMATICA

LinearRecurrence[{2, -7}, {1, 2}, 40] (* Harvey P. Dale, Nov 04 2011 *)

PROG

(Sage) [lucas_number1(n, 2, 7) for n in range(1, 18)] #  Zerinvary Lajos, Apr 23 2009

(PARI) x='x+O('x^30); Vec(x/(1-2*x+7*x^2)) \\ G. C. Greubel, Oct 22 2018

(MAGMA) I:=[1, 2]; [n le 2 select I[n] else 2*Self(n-1) - 7*Self(n-2): n in [1..30]]; // G. C. Greubel, Oct 22 2018

(GAP) a:=[1, 2];; for n in [3..30] do a[n]:=2*a[n-1]-7*a[n-2]; od; a; # Muniru A Asiru, Oct 23 2018

CROSSREFS

Sequence in context: A344546 A279719 A279672 * A028425 A224987 A024630

Adjacent sequences:  A089178 A089179 A089180 * A089182 A089183 A089184

KEYWORD

sign

AUTHOR

Simone Severini, Dec 08 2003

EXTENSIONS

Corrected by T. D. Noe, Dec 11 2006

Extended by T. D. Noe, May 23 2011

STATUS

approved

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Last modified June 25 10:28 EDT 2021. Contains 345453 sequences. (Running on oeis4.)