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A088138 Generalized Gaussian Fibonacci integers. 12
0, 1, 2, 0, -8, -16, 0, 64, 128, 0, -512, -1024, 0, 4096, 8192, 0, -32768, -65536, 0, 262144, 524288, 0, -2097152, -4194304, 0, 16777216, 33554432, 0, -134217728, -268435456, 0, 1073741824, 2147483648, 0, -8589934592, -17179869184, 0, 68719476736, 137438953472 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

The sequence 0,1,-2,0,8,-16,... has g.f. x/(1+2*x-4*x^2), a(n)=2^n*sin(2n*pi/3)/sqrt(3) and is the inverse binomial transform of sin(sqrt(3)*x)/sqrt(3): 0,1,-3,0,9,...

a(n+1) is the Hankel transform of A100192. - Paul Barry, Jan 11 2007

a(n+1) is the Trinomial transform of A010892: a(n+1) = Sum[Trinomial[n,k]A010892[k+1], {k, 0, 2n} ] where Trinomial[n, k] = trinomial coefficients (A027907); - Paul Barry, Sep 10 2007

a(n+1) is the Hankel transform of A100067. [From Paul Barry, Jun 16 2009]

1) a(n)=A131577*A128834 2) Binomial transform of 0,1,0,-3,0,9,0,-27, see A000244. 3) Sequence is identical to every 2n-th differences divided by (-3)^n. 4) a(3n)+a(3n+1)+a(3n+2)=3,-24,192,=3*A001018 signed.

5) For missing terms in a(n) see A013731=4*A001018. [From Paul Curtz, Oct 04 2009]

The coefficient of i of Q^n, where Q is the quaternion 1+i+j+k. Due to symmetry, also the coefficients of either j or k. - Stanislav Sykora, Jun 11 2012.

With different signs, 0, 1, -2, 0, 8, -16, 0, 64, -128, 0, 512, -1024,... is the Lucas U(-2,4) sequence. - R. J. Mathar, Jan 08 2013

LINKS

Table of n, a(n) for n=0..38.

Wikipedia, Lucas sequence

Index to sequences with linear recurrences with constant coefficients, signature (2,-4)

Index entries for Lucas sequences

FORMULA

G.f.: x/(1-2*x+4*x^2)

E.g.f. exp(x)*sin(sqrt(3)*x)/sqrt(3)

a(n) = 2*a(n-1)-4*a(n-2), a(0)=0, a(1)=1

a(n) = ((1+i*sqrt(3))^n-(1-i*sqrt(3))^n)/(2*i*sqrt(3))

a(n) = Im( (1+i*sqrt(3))^n/sqrt(3) ).

a(n) = sum(k=0..floor(n/2), C(n, 2*k+1)*(-3)^k ).

a(n) = a(n-1)+a(n-2)+2*a(n-3); a(n) = 2*a(n-1)-a(n-2)+2*a(n-3); a(n) = a(n-1)+2*a(n-2)-a(n-3)-a(n-4). - Paul Curtz, Oct 04 2009

E.g.f. exp(x)*sin(sqrt(3)*x)/sqrt(3) = G(0)*x^2 where G(k)= 1 + (3*k+2)/(2*x - 32*x^5/( 16*x^4 - 3*(k+1)*(3*k+2)*(3*k+4)*(3*k+5)/G(k+1))); (continued fraction, 3rd kind, 3-step). - Sergei N. Gladkovskii, Jul 26 2012

G.f.: x/(1-2*x+4*x^2) = 2*x^2*G(0) where G(k)= 1 + 1/(2*x - 32*x^5/(16*x^4 - 1/G(k+1))); (continued fraction, 3rd kind, 3-step). - Sergei N. Gladkovskii, Jul 27 2012

MATHEMATICA

Join[{a=0, b=1}, Table[c=2*b-4*a; a=b; b=c, {n, 100}]] (* Vladimir Joseph Stephan Orlovsky, Jan 17 2011*)

PROG

(Sage) [lucas_number1(n, 2, 4) for n in xrange(0, 39)] # [From Zerinvary Lajos, Apr 23 2009]

(PARI) /* lists powers of any quaternion) */

QuaternionToN(a, b, c, d, nmax) = {local (C); C = matrix(nmax+1, 4); C[1, 1]=1; for(n=2, nmax+1, C[n, 1]=a*C[n-1, 1]-b*C[n-1, 2]-c*C[n-1, 3]-d*C[n-1, 4]; C[n, 2]=b*C[n-1, 1]+a*C[n-1, 2]+d*C[n-1, 3]-c*C[n-1, 4]; C[n, 3]=c*C[n-1, 1]-d*C[n-1, 2]+a*C[n-1, 3]+b*C[n-1, 4]; C[n, 4]=d*C[n-1, 1]+c*C[n-1, 2]-b*C[n-1, 3]+a*C[n-1, 4]; ); return (C); } /* Stanislav Sykora, Jun 11 2012 */

CROSSREFS

Cf. A084102, A088137, A045873, A088139.

Sequence in context: A009794 A171402 A104506 * A186033 A120559 A120555

Adjacent sequences:  A088135 A088136 A088137 * A088139 A088140 A088141

KEYWORD

easy,sign

AUTHOR

Paul Barry, Sep 20 2003

STATUS

approved

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Last modified December 19 19:48 EST 2014. Contains 252239 sequences.