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A090592 (1,1) entry of powers of the orthogonal design shown below. 3
1, -5, -17, 1, 121, 235, -377, -2399, -2159, 12475, 40063, -7199, -294839, -539285, 985303, 5745601, 4594081, -31031045, -94220657, 28776001, 717096601, 1232761195, -2554153817, -13737635999, -9596195279, 76971061435, 221115489823, -96566450399, -1740941329559 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

   1  0  1  1  1  1  1  1

   0  1  1 -1  1 -1 -1  1

  -1 -1  1  0  1  1 -1 -1

  -1  1  0  1  1 -1  1 -1

  -1 -1 -1 -1  1  0  1  1

  -1  1 -1  1  0  1 -1  1

  -1  1  1 -1 -1  1  1  0

  -1 -1  1  1 -1 -1  0  1

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..1000

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

FORMULA

a(1) = 1, a(2) = -5, a(n) = 2*a(n-1) - 7*a(n-2). - Philippe Deléham, Mar 05 2012

G.f.: x*(1-7*x)/(1-2*x+7*x^2). - Philippe Deléham, Mar 05 2012

G.f.: G(0)/(2*x) -1/x, where G(k)= 1 + 1/(1 - x*(6*k+1)/(x*(6*k+7) + 1/G(k+1))); (continued fraction). - Sergei N. Gladkovskii, Jun 03 2013

MATHEMATICA

Rest[CoefficientList[Series[x*(1-7*x)/(1-2*x+7*x^2), {x, 0, 30}], x]] (* G. C. Greubel, Oct 22 2018 *)

PROG

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

(MAGMA) I:=[1, -5]; [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, -5];; 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

Cf. A089181.

Sequence in context: A160739 A092679 A277534 * A093558 A170866 A125636

Adjacent sequences:  A090589 A090590 A090591 * A090593 A090594 A090595

KEYWORD

sign,easy

AUTHOR

Simone Severini, Dec 08 2003

EXTENSIONS

Corrected and extended by Philippe Deléham, Mar 05 2012

STATUS

approved

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Last modified January 27 17:58 EST 2020. Contains 331296 sequences. (Running on oeis4.)