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 1-2 of 2 results.

A087433 Expansion of g.f.: (1-2*x)*(1-4*x+x^2)/((1-x)*(1-3*x)*(1-4*x)).

Original entry on oeis.org

1, 2, 6, 20, 70, 252, 926, 3460, 13110, 50252, 194446, 758100, 2973350, 11716252, 46333566, 183739940, 730176790, 2906358252, 11582386286, 46200404980, 184414199430, 736494536252, 2942491360606, 11759505089220, 47006639297270
Offset: 0

Views

Author

Paul Barry, Sep 02 2003

Keywords

Comments

Binomial transform of A087432. a(n+1) = 2*A085282(n).
Counts closed walks of length 2n at a vertex of the cyclic graph on 12 nodes C_12. - Herbert Kociemba, Jun 06 2004

Crossrefs

Programs

  • Magma
    [0^n/6+1/3+3^n/3+4^n/6: n in [0..30]]; // Vincenzo Librandi, Aug 12 2011
  • Mathematica
    CoefficientList[Series[(1-2x)(1-4x+x^2)/((1-x)(1-3x)(1-4x)),{x,0,30}],x] (* Harvey P. Dale, Nov 26 2014 *)

Formula

G.f.: (1-2*x)*(1-4*x+x^2)/((1-x)*(1-3*x)*(1-4*x)).
a(n) = 0^n/6 + 1/3 + 3^n/3 + 4^n/6.
a(n) = 8*a(n-1) - 19*a(n-2) + 12*a(n-3). - Wesley Ivan Hurt, Jul 11 2023

Extensions

Definition corrected by Herbert Kociemba, Jun 06 2004

A093379 Expansion of x(1-2x-2x^2)/((1+x)(1-2x)(1-3x)).

Original entry on oeis.org

0, 1, 2, 5, 12, 31, 82, 225, 632, 1811, 5262, 15445, 45652, 135591, 404042, 1206665, 3609072, 10805371, 32372422, 97029885, 290914892, 872395151, 2616486402, 7848061105, 23541387112, 70618568931, 211844521982, 635511196325
Offset: 0

Views

Author

Paul Barry, Apr 28 2004

Keywords

Comments

Binomial transform is A085280, with leading zero.

Crossrefs

Cf. A087432.

Programs

  • Mathematica
    CoefficientList[Series[x (1-2x-2x^2)/((1+x)(1-2x)(1-3x)),{x,0,30}],x] (* or *) LinearRecurrence[{4,-1,-6},{0,1,2,5},40] (* Harvey P. Dale, May 10 2019 *)

Formula

a(n)=3^n/12-(-1)^n/12+2^n/3-0^n/3;
a(n)=4a(n-1)-a(n-2)-6a(n-3).
a(n)=A015518(n)/3+A000079(n)/3-0^n/3.
Showing 1-2 of 2 results.