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 1-6 of 6 results.

A159288 Expansion of (1 + x + x^2)/(1 - x^2 - 2*x^3).

Original entry on oeis.org

1, 1, 2, 3, 4, 7, 10, 15, 24, 35, 54, 83, 124, 191, 290, 439, 672, 1019, 1550, 2363, 3588, 5463, 8314, 12639, 19240, 29267, 44518, 67747, 103052, 156783, 238546, 362887, 552112, 839979, 1277886, 1944203, 2957844, 4499975, 6846250, 10415663
Offset: 0

Views

Author

Creighton Dement, Apr 08 2009

Keywords

Comments

A floretion-generated sequence: 'i + 0.5('ij' + 'ik' + 'ji' + 'jk' + 'ki' + 'kj')
Starting with offset 1 the sequence appears to be the INVERT transform of (1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, ...). - Gary W. Adamson, Aug 27 2016

Crossrefs

Programs

  • Magma
    I:=[1, 1, 2]; [n le 3 select I[n] else Self(n-2) + 2*Self(n-2): n in [1..30]]; // G. C. Greubel, Jun 27 2018
  • Mathematica
    CoefficientList[Series[(1+x+x^2)/(1-x^2-2x^3),{x,0,50}],x]  (* Harvey P. Dale, Mar 09 2011 *)
    LinearRecurrence[{0, 1, 2}, {1, 1, 2}, 50] (* G. C. Greubel, Jun 27 2018 *)
  • PARI
    a(n)=([0,1,0; 0,0,1; 2,1,0]^n*[1;1;2])[1,1] \\ Charles R Greathouse IV, Aug 27 2016
    
  • PARI
    Vec((1 + x + x^2) / (1 - x^2 - 2*x^3) + O(x^40)) \\ Colin Barker, Apr 29 2019
    

Formula

a(n) = A159287(n) + A159287(n+1) + A159287(n+2). - R. J. Mathar, Apr 10 2009
a(n) = a(n-2) + 2*a(n-3) for n>2. - Colin Barker, Apr 29 2019
a(n)= A052947(n) + A052947(n-1) +A052947(n-2). - R. J. Mathar, Mar 23 2023

A159284 Expansion of x*(1+x)/(1-x^2-2*x^3).

Original entry on oeis.org

0, 1, 1, 1, 3, 3, 5, 9, 11, 19, 29, 41, 67, 99, 149, 233, 347, 531, 813, 1225, 1875, 2851, 4325, 6601, 10027, 15251, 23229, 35305, 53731, 81763, 124341, 189225, 287867, 437907, 666317, 1013641, 1542131, 2346275, 3569413, 5430537
Offset: 0

Views

Author

Creighton Dement, Apr 08 2009

Keywords

Comments

a(n) is the number of composition of n+1 into parts congruent to 0 or 2 modulo 3. - Joerg Arndt, Apr 21 2025

Crossrefs

Programs

  • Magma
    I:=[0,1,1]; [n le 3 select I[n] else Self(n-2) + 2*Self(n-3): n in [1..30]]; // G. C. Greubel, Jun 27 2018
  • Mathematica
    CoefficientList[Series[x (1+x)/(1-x^2-2x^3),{x,0,50}],x] (* or *) LinearRecurrence[ {0,1,2},{0,1,1},50] (* Harvey P. Dale, Jul 16 2013 *)
  • PARI
    a(n)=([0,1,0; 0,0,1; 2,1,0]^n*[0;1;1])[1,1] \\ Charles R Greathouse IV, Oct 03 2016
    

Formula

a(n) = abs(A078028(n-1)). - R. J. Mathar, Jul 05 2012
a(n) = a(n-2) + 2*a(n-3), a(0)=0, a(1) = a(2) =1. - G. C. Greubel, Apr 30 2017
a(n) = A052947(n-1)+A052947(n-2). - R. J. Mathar, Mar 23 2023

Extensions

Deleted certain dangerous or potentially dangerous links. - N. J. A. Sloane, Jan 30 2021

A159285 Expansion of (1+3*x)/(1-x^2-2*x^3).

Original entry on oeis.org

1, 3, 1, 5, 7, 7, 17, 21, 31, 55, 73, 117, 183, 263, 417, 629, 943, 1463, 2201, 3349, 5127, 7751, 11825, 18005, 27327, 41655, 63337, 96309, 146647, 222983, 339265, 516277, 785231, 1194807, 1817785, 2765269, 4207399, 6400839, 9737937, 14815637
Offset: 0

Views

Author

Creighton Dement, Apr 08 2009

Keywords

Comments

A floretion-generated sequence: 'i + 0.5('ij' + 'ik' + 'ji' + 'jk' + 'ki' + 'kj')

Crossrefs

Programs

  • Magma
    I:=[1,3,1]; [n le 3 select I[n] else Self(n-2) + 2*Self(n-3): n in [1..30]]; // G. C. Greubel, Jun 27 2018
  • Mathematica
    LinearRecurrence[{0, 1, 2}, {1, 3, 1}, 50] (* G. C. Greubel, Jun 27 2018 *)
    CoefficientList[Series[(1+3x)/(1-x^2-2x^3),{x,0,40}],x] (* Harvey P. Dale, Jan 21 2019 *)
  • PARI
    a(n)=([0,1,0; 0,0,1; 2,1,0]^n*[1;3;1])[1,1] \\ Charles R Greathouse IV, Oct 03 2016
    

Formula

a(n) = A052947(n) + 3*A052947(n-1). - R. J. Mathar, Mar 23 2023

A159286 Expansion of (x-1)^2/(1-x^2-2*x^3).

Original entry on oeis.org

1, -2, 2, 0, -2, 4, -2, 0, 6, -4, 6, 8, -2, 20, 14, 16, 54, 44, 86, 152, 174, 324, 478, 672, 1126, 1628, 2470, 3880, 5726, 8820, 13486, 20272, 31126, 47244, 71670, 109496, 166158, 252836, 385150, 585152
Offset: 0

Views

Author

Creighton Dement, Apr 08 2009

Keywords

Comments

A floretion-generated sequence: 'i + 0.5('ij' + 'ik' + 'ji' + 'jk' + 'ki' + 'kj').

Crossrefs

Programs

  • Magma
    I:=[1, -2, 2]; [n le 3 select I[n] else Self(n-2) + 2*Self(n-3): n in [1..30]]; // G. C. Greubel, Jun 27 2018
  • Mathematica
    CoefficientList[Series[(x-1)^2/(1-x^2-2*x^3),{x,0,40}],x] (* or *) LinearRecurrence[{0,1,2},{1,-2,2},40]  (* Harvey P. Dale, Apr 24 2011 *)
  • PARI
    a(n)=([0,1,0; 0,0,1; 2,1,0]^n*[1;-2;2])[1,1] \\ Charles R Greathouse IV, Oct 03 2016
    

Formula

a(n) = A159288(n) - 3*A159287(n+1). - R. J. Mathar, Apr 10 2009
a(1)=1, a(2)=-2, a(3)=2, a(n) = 1*a(n-2) + 2*a(n-3) for n >= 3. - Harvey P. Dale, Apr 24 2011
a(n) = A078026(n)-A078026(n-1). - R. J. Mathar, Mar 23 2023

A107853 Expansion of g.f. x*(x-1)*(x+1)^3/((2*x^3+x^2-1)*(x^4+1)).

Original entry on oeis.org

0, 1, 2, 1, 2, 3, 2, 7, 10, 13, 26, 33, 50, 83, 114, 183, 282, 413, 650, 977, 1474, 2275, 3426, 5223, 7978, 12077, 18426, 28033, 42578, 64883, 98642, 150039, 228410, 347325, 528490, 804145, 1223138, 1861123, 2831426, 4307399, 6553674, 9970253
Offset: 0

Views

Author

Creighton Dement, May 25 2005

Keywords

Comments

Floretion Algebra Multiplication Program, FAMP Code: - 2basejforzapseq[(.5i' + .5j' + .5'ki' + .5'kj')*(.5'i + .5'j + .5'ik' + .5'jk')], 1vesforzap = A000004

Crossrefs

Programs

  • Mathematica
    LinearRecurrence[{0,1,2,-1,0,1,2},{0,1,2,1,2,3,2},50] (* Harvey P. Dale, Jan 24 2018 *)

Formula

a(n) = 2*A159287(n) + A091337(n+6).

A167434 Diagonal sums of the Riordan array (1-4*x+4*x^2, x*(1-2*x)) (A167431).

Original entry on oeis.org

1, -4, 5, -6, 13, -16, 25, -42, 57, -92, 141, -206, 325, -488, 737, -1138, 1713, -2612, 3989, -6038, 9213, -14016, 21289, -32442, 49321, -75020, 114205, -173662, 264245, -402072, 611569, -930562, 1415713, -2153700, 3276837, -4985126, 7584237
Offset: 0

Views

Author

Paul Barry, Nov 03 2009

Keywords

Crossrefs

Programs

  • Magma
    I:=[1,-4,5]; [n le 3 select I[n] else Self(n-2) - 2*Self(n-3): n in [1..40]]; // G. C. Greubel, Jun 27 2018
  • Mathematica
    LinearRecurrence[{0, 1, -2}, {1, -4, 5}, 100] (* G. C. Greubel, Jun 13 2016 *)
    CoefficientList[Series[(1-4x+4x^2)/(1-x^2+2x^3),{x,0,40}],x] (* Harvey P. Dale, Nov 08 2022 *)
  • PARI
    x='x+O('x^40); Vec((1-4*x+4*x^2)/(1-x^2+2*x^3)) \\ G. C. Greubel, Jun 27 2018
    

Formula

G.f.: (1-2*x)^2/(1-x^2+2*x^3).
a(n) = (-1)^n*A052947(n+4). - R. J. Mathar, Jun 24 2024
Showing 1-6 of 6 results.