A089181 (1,3) entry of powers of the orthogonal design shown in A090592.

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

Offset: 1

Author

Simone Severini, Dec 08 2003

Keywords

• sign

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000
• Index entries for linear recurrences with constant coefficients, signature (2, -7).

Programs

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

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

Mathematica

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

PARI

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

Sage

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

Formula

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

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

Extensions

Corrected by T. D. Noe, Dec 11 2006

Extended by T. D. Noe, May 23 2011