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A001590 Tribonacci numbers: a(n) = a(n-1) + a(n-2) + a(n-3) with a(0)=0, a(1)=1, a(2)=0.
(Formerly M0784 N0296)
109
0, 1, 0, 1, 2, 3, 6, 11, 20, 37, 68, 125, 230, 423, 778, 1431, 2632, 4841, 8904, 16377, 30122, 55403, 101902, 187427, 344732, 634061, 1166220, 2145013, 3945294, 7256527, 13346834, 24548655, 45152016, 83047505, 152748176, 280947697, 516743378, 950439251 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

Dimensions of the homogeneous components of the higher order peak algebra associated to cubic roots of unity (Hilbert series = 1 + 1*t + 2*t^2 + 3*t^3 + 6*t^4 + 11*t^5 ...). - Jean-Yves Thibon (jyt(AT)univ-mlv.fr), Oct 22 2006

Starting with offset 3: (1, 2, 3, 6, 11, 10, 37,...) = row sums of triangle A145579. - Gary W. Adamson, Oct 13 2008

Starting (1, 2, 3, 6, 1l,...) = INVERT transform of the periodic sequence (1, 1, 0, 1, 1, 0, 1, 1, 0,...). - Gary W. Adamson, May 04 2009

The comment of May 04 2009 is equivalent to: The numbers of ordered compositions of n using integers that are not multiples of 3 is equal to (1, 2, 3, 6, 11, ...) for n = (1, 2, 3,...). - Gary W. Adamson, May 13 2013

Primes in the sequence are 2, 3, 11, 37, 634061, 7256527, 1424681173049, ... in A231574. - R. J. Mathar, Aug 09 2012

Pisano period lengths: 1, 2, 13, 8, 31, 26, 48, 16, 39, 62,110,104,168, 48,403, 32, 96, 78, 360, 248, ... . - R. J. Mathar, Aug 10 2012

a(n+1) is the top left entry of the n-th power of any of 3 X 3 matrices [0, 1, 0; 1, 1, 1; 1, 0, 0], [0, 1, 1; 1, 1, 0; 0, 1, 0], [0, 1, 1; 0, 0, 1; 1, 0, 1] or [0, 0, 1; 1, 0, 0; 1, 1, 1]. - R. J. Mathar, Feb 03 2014

a(n+3) equals the number of n-length binary words avoiding runs of zeros of lengths 3i+2, (i=0,1,2,...). - Milan Janjic, Feb 26 2015

Sums of pairs of successive terms of A000073. - N. J. A. Sloane, Oct 30 2016

REFERENCES

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

T. D. Noe, Table of n, a(n) for n = 0..200

Barry Balof, Restricted tilings and bijections, J. Integer Seq. 15 (2012), no. 2, Article 12.2.3, 17 pp.

Matthias Beck, Neville Robbins, Variations on a Generatingfunctional Theme: Enumerating Compositions with Parts Avoiding an Arithmetic Sequence, arXiv:1403.0665 [math.NT] (2014)

Martin Burtscher, Igor Szczyrba, Rafał Szczyrba, Analytic Representations of the n-anacci Constants and Generalizations Thereof, Journal of Integer Sequences, Vol. 18 (2015), Article 15.4.5.

M. Feinberg, Fibonacci-Tribonacci, Fib. Quart. 1(3) (1963), 71-74.

M. Feinberg, New slants, Fib. Quart. 2 (1964), 223-227.

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 401

D. Krob and J.-Y. Thibon, Higher order peak algebras

Bo Tan and Zhi-Ying Wen, Some properties of the Tribonacci sequence, European Journal of Combinatorics, 28 (2007) 1703-1719.

M. E. Waddill and L. Sacks, Another generalized Fibonacci sequence, Fib. Quart., 5 (1967), 209-222.

Eric Weisstein's World of Mathematics, Tribonacci Number

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

FORMULA

G.f.: x*(1-x)/(1-x-x^2-x^3).

Limit a(n)/a(n-1)=x where x^3=1+x+x^2, x=1.839286755.... Let T(n)=A000073=0, 0, 1, 1, 2, 4, 7, 13... x^0=1 and for n>0 x^n=T(n-1)+a(n)*x+T(n)*x^2.

a(3*n) = Sum_{k+l+m=n} (n!/k!l!m!)*a(l+2*m). Example: a(12)=a(8)+4a(7)+10a(6)+16a(5)+19a(4)+16a(3)+10a(2)+4a(1)+a(0) The coefficients are the trinomial coefficients. T(n) and T(n-1) also satisfy this equation. (T(-1)=1)

a(n)=A000073(n+1)-A000073(n); a(n)=A000073(n-1)+A000073(n-2) for n>1; A000213(n-2)=a(n+1)-a(n) for n>1. - Reinhard Zumkeller, May 22 2006

a(n)+a(n+1)=A000213(n). - Philippe Deléham, Sep 25 2006

If p[1]=0, p[i]=2, (i>1), and if A is Hessenberg matrix of order n defined by: A[i,j]=p[j-i+1], (i<=j), A[i,j]=-1, (i=j+1), and A[i,j]=0 otherwise. Then, for n>=1, a(n+1)=det A. - Milan Janjic, May 02 2010

For n>=4, a(n)=2*a(n-1)-a(n-4). - Bob Selcoe, Feb 18 2014

a(-1-n) = -A078046(n). - Michael Somos, Jun 01 2014

EXAMPLE

a(12)=a(11)+a(10)+a(9): 230=125+68+37.

G.f. = x + x^3 + 2*x^4 + 3*x^5 + 6*x^6 + 11*x^7 + 20*x^8 + 37*x^9 + 68*x^10 + ...

MATHEMATICA

a=0; b=1; c=0; lst={a, b, c}; Do[d=a+b+c; AppendTo[lst, d]; a=b; b=c; c=d, {n, 5!}]; lst (* Vladimir Joseph Stephan Orlovsky, Sep 30 2008 *)

LinearRecurrence[{1, 1, 1}, {0, 1, 0}, 50] (* Vladimir Joseph Stephan Orlovsky, Jan 28 2012 *)

PROG

(PARI) a(n)=([0, 1, 0; 0, 0, 1; 1, 1, 1]^n*[0; 1; 0])[1, 1] \\ Charles R Greathouse IV, Jul 28 2015

(Sage)

def A001590():

    W = [0, 1, 0]

    while True:

        yield W[0]

        W.append(sum(W))

        W.pop(0)

a = A001590(); print [a.next() for _ in range(38)] # Peter Luschny, Sep 12 2016

CROSSREFS

Cf. A000045, A000073, A027907, A001590, A027053, A078042, A145579.

Sequence in context: A010033 A065615 A054182 * A078042 A115792 A054177

Adjacent sequences:  A001587 A001588 A001589 * A001591 A001592 A001593

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Henry Bottomley, Jun 26 2001

Additional comments from Miklos Kristof, Jul 03 2002

STATUS

approved

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Last modified March 24 00:18 EDT 2017. Contains 283983 sequences.