cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-10 of 12 results. Next

A075115 Binomial transform of A073145: a(n)=Sum(binomial(n,k)*A073145(k),(k=0,..,n)).

Original entry on oeis.org

3, 2, 0, 2, 8, 12, 12, 16, 32, 56, 80, 112, 176, 288, 448, 672, 1024, 1600, 2496, 3840, 5888, 9088, 14080, 21760, 33536, 51712, 79872, 123392, 190464, 293888, 453632, 700416, 1081344, 1669120, 2576384, 3977216, 6139904, 9478144, 14630912
Offset: 0

Views

Author

Mario Catalani (mario.catalani(AT)unito.it), Sep 02 2002

Keywords

Comments

a(n) is nonnegative since the real root of x^3-2*x^2+2*x-2 is dominant. - Michael Somos, Feb 28 2007

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[(3-4*x+2*x^2)/(1-2*x+2*x^2-2*x^3), {x, 0, 40}], x]
    LinearRecurrence[{2,-2,2},{3,2,0},40] (* Harvey P. Dale, Jan 24 2019 *)
  • PARI
    {a(n)= if(n<0, 0, polsym( x^3 -2*x^2 +2*x -2, n) [n+1])} /* Michael Somos, Feb 28 2007 */

Formula

a(n)=2a(n-1)-2a(n-2)+2a(n-3), a(0)=3, a(1)=2, a(2)=0.
G.f.: (3 - 4*x + 2*x^2)/(1 - 2*x + 2*x^2 - 2*x^3).
a(n) = 3*A077943(n) -4*A077943(n-1) +2*A077943(n-2). - R. J. Mathar, Mar 13 2021

A075092 Sum of generalized tribonacci numbers (A001644) and reflected generalized tribonacci numbers (A073145).

Original entry on oeis.org

6, 0, 2, 12, 6, 20, 50, 56, 134, 264, 402, 836, 1542, 2652, 5154, 9392, 16902, 31824, 58082, 106172, 197126, 360932, 662994, 1223784, 2245766, 4130520, 7606770, 13976436, 25711622, 47310252, 86978370, 160002656, 294324230, 541249952
Offset: 0

Views

Author

Mario Catalani (mario.catalani(AT)unito.it), Aug 31 2002

Keywords

Comments

Conjecture: a(n) >= 0.
For n > 2, a(n) is the number of cyclic sequences (q1, q2, ..., qn) consisting of zeros, ones and twos such that each triple contains 0 and 1 at least once, provided the positions of the zeros and ones are fixed on a circle. For example, a(5)=20 because only the sequences (00101), (01001), (01010), (01011), (01012), (01021), (01101), (01201), (02101), (20101) and those obtained from them by exchanging 0 and 1 contain 0 and 1 in each triple (including triples q4, q5, q1 and q5, q1, q2). For n = 1, 2 the statement is still true provided we allow the sequence to wrap around itself on a circle. E.g., a(2) = 2 since only sequences 01 and 10 can be wrapped so one obtains (010) and (101), respectively. - Wojciech Florek, Nov 25 2021

Crossrefs

Programs

  • Magma
    R:=PowerSeriesRing(Integers(), 40); Coefficients(R!( (6-4*x^2-12*x^3-2*x^4)/(1-x^2-4*x^3-x^4+x^6) ));  // G. C. Greubel, Apr 13 2019
    
  • Mathematica
    CoefficientList[Series[(6-4*x^2-12*x^3-2*x^4)/(1-x^2-4*x^3-x^4+x^6), {x, 0, 40}], x]
  • PARI
    my(x='x+O('x^40)); Vec((6-4*x^2-12*x^3-2*x^4)/(1-x^2-4*x^3-x^4+x^6)) \\ G. C. Greubel, Apr 13 2019
    
  • Sage
    ((6-4*x^2-12*x^3-2*x^4)/(1-x^2-4*x^3-x^4+x^6)).series(x, 40).coefficients(x, sparse=False) # G. C. Greubel, Apr 13 2019

Formula

a(n) = a(n-2) + 4*a(n-3) + a(n-4) - a(n-6), a(0)=6, a(1)=0, a(2)=2, a(3)=12, a(4)=6, a(5)=20.
G.f.: (6 - 4*x^2 - 12*x^3 - 2*x^4)/(1 - x^2 - 4*x^3 - x^4 + x^6).

A073498 Binomial transform of A073145.

Original entry on oeis.org

3, 4, 4, -2, -24, -76, -164, -248, -160, 520, 2544, 6736, 12720, 15552, -640, -70432, -246784, -565824, -923456, -792448, 1239296, 7864960, 22439168, 45045504, 61276928, 19713024, -198718464, -790598144, -1930655744, -3376471040, -3503145984, 2384930816, 23805657088
Offset: 0

Views

Author

Mario Catalani (mario.catalani(AT)unito.it), Aug 03 2002

Keywords

Crossrefs

Cf. A073145.

Programs

  • Mathematica
    CoefficientList[Series[(3-8*x+6*x^2)/(1-4*x+6*x^2-2*x^3), {x, 0, 50}], x]

Formula

O.g.f.: (3-8x+6x^2)/(1-4x+6x^2-2x^3); a(n)=4a(n-1)-6a(n-2)+2a(n-3), a(0)=3, a(1)=4, a(2)=4

A073702 a(n) = A073145(n)^2.

Original entry on oeis.org

9, 1, 1, 25, 25, 1, 121, 225, 9, 529, 1681, 441, 1849, 11025, 6889, 4225, 64009, 73441, 2209, 326041, 632025, 31329, 1413721, 4669921, 1320201, 4844401, 30371121, 19882681, 10582009, 174847729, 208196041, 4190209, 882030601, 1770810561
Offset: 0

Views

Author

Mario Catalani (mario.catalani(AT)unito.it), Aug 04 2002

Keywords

Crossrefs

Programs

  • Magma
    R:=PowerSeriesRing(Integers(), 40); Coefficients(R!( (9+x+ 10*x^2-28*x^3-7*x^4-x^5)/(1+x^2-6*x^3-3*x^4-2*x^5+x^6) )); // G. C. Greubel, Apr 23 2019
    
  • Mathematica
    CoefficientList[Series[(9+x+10x^2-28x^3-7x^4-x^5)/(1+x^2-6x^3-3x^4-2x^5 +x^6), {x, 0, 40}], x]
    LinearRecurrence[{0,-1,6,3,2,-1},{9,1,1,25,25,1},40] (* Harvey P. Dale, Feb 14 2015 *)
  • PARI
    my(x='x+O('x^40)); Vec((9+x+10*x^2-28*x^3-7*x^4-x^5)/(1+x^2-6*x^3 -3*x^4-2*x^5+x^6)) \\ G. C. Greubel, Apr 23 2019
    
  • Sage
    ((9+x+10*x^2-28*x^3-7*x^4-x^5)/(1+x^2-6*x^3-3*x^4-2*x^5+x^6) ).series(x, 40).coefficients(x, sparse=False) # G. C. Greubel, Apr 23 2019

Formula

a(n) = -a(n-2) + 6*a(n-3) + 3*a(n-4) + 2*a(n-5) - a(n-6) with a(0)=9, a(1)=1, a(2)=1, a(3)=25, a(4)=25, a(5)=1.
G.f.: (9+x+10*x^2-28*x^3-7*x^4-x^5)/(1+x^2-6*x^3-3*x^4-2*x^5+x^6).
a(n) = 2*A001644(n) + A073496(n).

A074585 a(n)= Sum_{j=0..floor(n/2)} A073145(2*j + q), where q = 2*(n/2 - floor(n/2)).

Original entry on oeis.org

3, -1, 2, 4, -3, 3, 8, -12, 11, 11, -30, 32, 13, -73, 96, -8, -157, 263, -110, -308, 685, -485, -504, 1676, -1653, -525, 3858, -4984, 605, 8239, -13824, 6192, 15875, -35889, 26210, 25556, -87651, 88307, 24904, -200860, 264267, -38501, -426622
Offset: 0

Views

Author

Mario Catalani (mario.catalani(AT)unito.it), Aug 28 2002

Keywords

Comments

a(n) is the convolution of A073145(n) with the sequence (1,0,1,0,1,0, ...).
a(n) is also the sum of the reflected (see A074058) sequence of the generalized tribonacci sequence (A001644).

Crossrefs

Programs

  • Magma
    R:=PowerSeriesRing(Integers(), 50); Coefficients(R!( (3+2*x+x^2)/(1+x-2*x^3-x^4+x^5) )); // G. C. Greubel, Apr 13 2019
    
  • Mathematica
    CoefficientList[ Series[(3+2*x+x^2)/(1+x-2*x^3-x^4+x^5), {x, 0, 50}], x]
  • PARI
    my(x='x+O('x^50)); Vec((3+2*x+x^2)/(1+x-2*x^3-x^4+x^5)) \\ G. C. Greubel, Apr 13 2019
    
  • Sage
    ((3+2*x+x^2)/(1+x-2*x^3-x^4+x^5)).series(x, 50).coefficients(x, sparse=False) # G. C. Greubel, Apr 13 2019

Formula

a(n) = -a(n-1) + 2*a(n-3) + a(n-4) - a(n-5), a(0) = 3, a(1) = -1, a(2) = 2, a(3) = 4, a(4) = -3.
G.f.: (3 + 2*x + x^2)/(1 + x - 2*x^3 - x^4 + x^5).

Extensions

More terms from Robert G. Wilson v, Aug 29 2002

A075419 Convolution of A073145 with A056594.

Original entry on oeis.org

3, -1, -4, 6, -1, -7, 12, -8, -9, 31, -32, -10, 75, -95, 8, 160, -261, 111, 308, -682, 487, 505, -1676, 1656, 527, -3857, 4984, -602, -8237, 13825, -6192, -15872, 35891, -26209, -25556, 87654, -88305, -24903, 200860, -264264, 38503, 426623, -729392, 341270, 814747, -1885407, 1411928, 1288224
Offset: 0

Views

Author

Mario Catalani (mario.catalani(AT)unito.it), Sep 17 2002

Keywords

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[(3 + 2x + x^2)/(1 + x + 2x^2 + x^4 - x^5), {x, 0, 50}], x]
    LinearRecurrence[{-1,-2,0,-1,1},{3,-1,-4,6,-1},50] (* Harvey P. Dale, Jul 27 2019 *)

Formula

a(n) = -a(n-1) - 2*a(n-2) - a(n-4) + a(n-5); a(0)=3, a(1)=-1, a(2)=-4, a(3)=6, a(4)=-1.
G.f.: (3 + 2*x + x^2)/(1 + x + 2*x^2 + x^4 - x^5).

A001644 a(n) = a(n-1) + a(n-2) + a(n-3), a(0)=3, a(1)=1, a(2)=3.

Original entry on oeis.org

3, 1, 3, 7, 11, 21, 39, 71, 131, 241, 443, 815, 1499, 2757, 5071, 9327, 17155, 31553, 58035, 106743, 196331, 361109, 664183, 1221623, 2246915, 4132721, 7601259, 13980895, 25714875, 47297029, 86992799, 160004703, 294294531, 541292033, 995591267, 1831177831
Offset: 0

Views

Author

Keywords

Comments

For n >= 3, a(n) is the number of cyclic sequences consisting of n zeros and ones that do not contain three consecutive ones provided the positions of the zeros and ones are fixed on a circle. This is proved in Charalambides (1991) and Zhang and Hadjicostas (2015). For example, a(3)=7 because only the sequences 110, 101, 011, 001, 010, 100 and 000 avoid three consecutive ones. (For n=1,2 the statement is still true provided we allow the sequence to wrap around itself on a circle.) - Petros Hadjicostas, Dec 16 2016
For n >= 3, also the number of dominating sets on the n-cycle graph C_n. - Eric W. Weisstein, Mar 30 2017
For n >= 3, also the number of minimal dominating sets and maximal irredundant sets on the n-sun graph. - Eric W. Weisstein, Jul 28 and Aug 17 2017
For n >= 3, also the number of minimal edge covers in the n-web graph. - Eric W. Weisstein, Aug 03 2017
For n >= 1, also the number of ways to tile a bracelet of length n with squares, dominoes, and trominoes. - Ruijia Li and Greg Dresden, Sep 14 2019
If n is prime, then a(n)-1 is a multiple of n ; a counterexample for the converse is given by n = 182. - Robert FERREOL, Apr 03 2024

Examples

			G.f. = 3 + x + 3*x^2 + 7*x^3 + 11*x^4 + 21*x^5 + 39*x^6 + 71*x^7 + 131*x^8 + ...
		

References

  • Miklos Bona, editor, Handbook of Enumerative Combinatorics, CRC Press, 2015, page 500.
  • G. Everest, A. van der Poorten, I. Shparlinski and T. Ward, Recurrence Sequences, Amer. Math. Soc., 2003; see esp. p. 255.
  • 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).

Crossrefs

Cf. A000073, A073145, A106293 (Pisano periods), A073728 (partial sums).
Cf. A058265.

Programs

  • GAP
    a:=[3,1,3];; for n in [4..40] do a[n]:=a[n-1]+a[n-2]+a[n-3]; od; a; # Muniru A Asiru, Dec 18 2018
    
  • Haskell
    a001644 n = a001644_list !! n
    a001644_list = 3 : 1 : 3 : zipWith3 (((+) .) . (+))
                   a001644_list (tail a001644_list) (drop 2 a001644_list)
    -- Reinhard Zumkeller, Apr 13 2014
    
  • Magma
    I:=[3,1,3]; [n le 3 select I[n] else Self(n-1)+Self(n-2)+ Self(n-3): n in [1..40]]; // Vincenzo Librandi, Aug 04 2017
    
  • Maple
    A001644:=-(1+2*z+3*z**2)/(z**3+z**2+z-1); # Simon Plouffe in his 1992 dissertation; gives sequence except for the initial 3
    A001644 :=proc(n)
        option remember;
        if n <= 2 then
            1+2*modp(n+1,2)
        else
            procname(n-1)+procname(n-2)+procname(n-3);
        end if;
    end proc:
    seq(A001644(n),n=0..80) ;
  • Mathematica
    a[x_]:= a[x] = a[x-1] +a[x-2] +a[x-3]; a[0] = 3; a[1] = 1; a[2] = 3; Array[a, 40, 0]
    a[n_]:= n*Sum[Sum[Binomial[j, n-3*k+2*j]*Binomial[k, j], {j,n-3*k,k}]/k, {k, n}]; a[0] = 3; Array[a, 40, 0] (* Robert G. Wilson v, Feb 24 2011 *)
    LinearRecurrence[{1, 1, 1}, {3, 1, 3}, 40] (* Vladimir Joseph Stephan Orlovsky, Feb 08 2012 *)
    Table[RootSum[-1 - # - #^2 + #^3 &, #^n &], {n, 0, 40}] (* Eric W. Weisstein, Mar 30 2017 *)
    RootSum[-1 - # - #^2 + #^3 &, #^Range[0, 40] &] (* Eric W. Weisstein, Aug 17 2017 *)
  • PARI
    {a(n) = if( n<0, polsym(1 - x - x^2 - x^3, -n)[-n+1], polsym(1 + x + x^2 - x^3, n)[n+1])}; /* Michael Somos, Nov 02 2002 */
    
  • PARI
    my(x='x+O('x^40)); Vec((3-2*x-x^2)/(1-x-x^2-x^3)) \\ Altug Alkan, Apr 19 2018
    
  • SageMath
    ((3-2*x-x^2)/(1-x-x^2-x^3)).series(x, 40).coefficients(x, sparse=False) # G. C. Greubel, Mar 22 2019

Formula

Binet's formula: a(n) = r1^n + r2^n + r3^n, where r1, r2, r3 are the roots of the characteristic polynomial 1 + x + x^2 - x^3, see A058265.
a(n) = A000073(n) + 2*A000073(n-1) + 3*A000073(n-2).
G.f.: (3-2*x-x^2)/(1-x-x^2-x^3). - Miklos Kristof, Jul 29 2002
a(n) = n*Sum_{k=1..n} Sum_{j=n-3*k..k} binomial(j, n-3*k+2*j)*binomial(k,j)/k, n > 0, a(0)=3. - Vladimir Kruchinin, Feb 24 2011
a(n) = a(n-1) + a(n-2) + a(n-3), a(0)=3, a(1)=1, a(2)=3. - Harvey P. Dale, Feb 01 2015
a(n) = A073145(-n). for all n in Z. - Michael Somos, Dec 17 2016
Sum_{k=0..n} k*a(k) = (n*a(n+3) - a(n+2) - (n+1)*a(n+1) + 4)/2. - Yichen Wang, Aug 30 2020
a(n) = Trace(M^n), where M = [0, 0, 1; 1, 0, 1; 0, 1, 1] is the companion matrix to the monic polynomial x^3 - x^2 - x - 1. It follows that the sequence satisfies the Gauss congruences: a(n*p^r) == a(n*p^(r-1)) (mod p^r) for positive integers n and r and all primes p. See Zarelua. - Peter Bala, Dec 29 2022

Extensions

Edited by Mario Catalani (mario.catalani(AT)unito.it), Jul 17 2002
Deleted certain dangerous or potentially dangerous links. - N. J. A. Sloane, Jan 30 2021

A075298 Inverted (definition in A075193) generalized tribonacci numbers A001644.

Original entry on oeis.org

1, 1, -5, 5, 1, -11, 15, -3, -23, 41, -21, -43, 105, -83, -65, 253, -271, -47, 571, -795, 177, 1189, -2161, 1149, 2201, -5511, 4459, 3253, -13223, 14429, 2047, -29699, 42081, -10335, -61445, 113861, -62751, -112555, 289167, -239363, -162359, 690889, -767893, -85355, 1544137, -2226675, 597183, 3173629
Offset: 0

Views

Author

Mario Catalani (mario.catalani(AT)unito.it), Sep 13 2002

Keywords

Comments

a(n) = -C(n+1), C(n)=reflected generalized tribonacci numbers A073145.

Crossrefs

Programs

  • GAP
    a:=[1,1,-5];; for n in [4..50] do a[n]:=-a[n-1]-a[n-2]+a[n-3]; od; a; # G. C. Greubel, Apr 09 2019
  • Magma
    R:=PowerSeriesRing(Integers(), 50); Coefficients(R!( (1+2*x-3*x^2)/(1+x+x^2-x^3) )); // G. C. Greubel, Apr 09 2019
    
  • Mathematica
    CoefficientList[Series[(1+2x-3x^2)/(1+x+x^2-x^3), {x, 0, 50}], x]
  • PARI
    my(x='x+O('x^50)); Vec((1+2*x-3*x^2)/(1+x+x^2-x^3)) \\ G. C. Greubel, Apr 09 2019
    
  • Sage
    ((1+2*x-3*x^2)/(1+x+x^2-x^3)).series(x, 50).coefficients(x, sparse=False) # G. C. Greubel, Apr 09 2019
    

Formula

a(n) = -a(n-1) - a(n-2) + a(n-3), a(0)=1, a(1)=1, a(2)=-5.
G.f.: (1+2*x-3*x^2)/(1+x+x^2-x^3).
a(n) = A078046(n) + 3*A078046(n-1). - R. J. Mathar, Sep 20 2020

A105580 a(n+3) = a(n) - a(n+1) - a(n+2); a(0) = -5, a(1) = 6, a(2) = 0.

Original entry on oeis.org

-5, 6, 0, -11, 17, -6, -22, 45, -29, -38, 112, -103, -47, 262, -318, 9, 571, -898, 336, 1133, -2367, 1570, 1930, -5867, 5507, 2290, -13664, 16881, -927, -29618, 47426, -18735, -58309, 124470, -84896, -97883, 307249, -294262, -110870, 712381, -895773, 72522, 1535632, -2503927, 1040817, 2998742
Offset: 0

Views

Author

Creighton Dement, Apr 14 2005

Keywords

Comments

Floretion Algebra Multiplication Program, FAMP Code: 2tesforseq[.5'j + .5'k + .5j' + .5k' + .5'ii' + .5e], 1vesforseq = A000004, ForType: 1A.

Examples

			This sequence was generated using the same floretion which generated the sequences A105577, A105578, A105579, etc.. However, in this case a force transform was applied. [Specifically, (a(n)) may be seen as the result of a tesfor-transform of the zero-sequence A000004 with respect to the floretion given in the program code.]
		

Crossrefs

Programs

  • Mathematica
    Transpose[NestList[Join[Rest[#],ListCorrelate[ {1,-1,-1}, #]]&,{-5,6,0},50]][[1]]  (* Harvey P. Dale, Mar 14 2011 *)
    CoefficientList[Series[(5-x-x^2)/(x^3-x^2-x-1),{x,0,50}],x]  (* Harvey P. Dale, Mar 14 2011 *)

Formula

G.f. (5-x-x^2)/(x^3-x^2-x-1)
a(n) = A078046(n-1) - A073145(n+3).
a(n) = -5*A057597(n+2) + A057597(n+1)+A057597(n). - R. J. Mathar, Oct 25 2022

A190913 Sequence A190914 evaluated at the negative index -n.

Original entry on oeis.org

5, 0, 2, 9, 2, 10, 29, 14, 50, 99, 82, 220, 365, 416, 926, 1429, 1954, 3842, 5825, 8778, 15922, 24299, 38414, 66240, 102533, 165560, 276954, 434745, 707394, 1163074, 1846069, 3008302, 4900546, 7839115, 12762378, 20694684, 33271421, 54081272, 87516358, 141133157, 229065490, 370410810, 598383689, 970090922, 1568482962
Offset: 0

Views

Author

Reikku Kulon, May 23 2011

Keywords

Crossrefs

Programs

Formula

From R. J. Mathar, Jun 05 2011: (Start)
a(n) = A190914(-n).
G.f.: ( 5-3*x^2-6*x^3 ) / ( (x^2+x-1)*(x^3-x^2-x-1) ). (End)
a(n) = A000032(n) + A073145(n). - R. J. Mathar, Jun 05 2011
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