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 1-3 of 3 results.

A103748 Triangle read by rows, based on the morphism f: 1->{2}, 2->{3}, 3->{3,3,2,1}. First row is 1. If current row is a,b,c,..., then the next row is a,b,c,...,f(a),f(b),f(c),...

Original entry on oeis.org

1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 3, 3, 2, 1, 1, 2, 2, 3, 2, 3, 3, 3, 3, 2, 1, 2, 3, 3, 3, 3, 2, 1, 3, 3, 3, 2, 1, 3, 3, 2, 1, 3, 3, 2, 1, 3, 3, 2, 1, 3, 2, 1, 2, 2, 3, 2, 3, 3, 3, 3, 2, 1, 2, 3, 3, 3, 3, 2, 1, 3, 3, 3, 2, 1, 3, 3, 2, 1, 3, 3, 2, 1, 3, 3, 2, 1, 3, 2, 2, 3, 3, 3, 3, 2, 1, 3, 3, 3, 2, 1, 3
Offset: 0

Views

Author

Roger L. Bagula, Mar 28 2005

Keywords

Comments

Kenyon tile substitution sequence.

Crossrefs

Programs

  • Mathematica
    s[n_] := n /. {1 -> 2, 2 -> 3, 3 -> {3, 3, 2, 1}}; t[a_] := Join[a, Flatten[s /@ a]]; Flatten[ NestList[t, {1}, 5]]

A103749 Expansion of x*(1+2*x)/(1+x+x^2-2*x^3).

Original entry on oeis.org

0, 1, 1, -2, 3, 1, -8, 13, -3, -26, 55, -35, -72, 217, -215, -146, 795, -1079, -8, 2677, -4827, 2134, 8047, -19835, 16056, 19873, -75599, 87838, 27507, -266543, 414712, -93155, -854643, 1777222, -1108889, -2377619, 7040952, -6881111, -4915079, 25878094, -34725237, -983015
Offset: 0

Views

Author

Roger L. Bagula, Mar 28 2005

Keywords

Comments

Insert n=3, p=2, q=-1 and r=1 in Kenyon's characteristic polynomial x^n-p*x^(n-1)+q*x+r=0 .

Crossrefs

Cf. A099206.

Programs

  • Mathematica
    LinearRecurrence[{-1,-1,2},{0,1,1},50] (* Harvey P. Dale, Jul 23 2013 *)

Formula

a(n) = -a(n-1)-a(n-2)+2*a(n-3) = A077975(n-1)+2*A077975(n-2).

Extensions

Edited, replaced by signed variant by the Assoc. Eds. of the OEIS - Jul 31 2010

A103750 Expansion of (1+2*x^3)/(1-x+x^3-2*x^4).

Original entry on oeis.org

1, 1, 1, 2, 3, 4, 4, 5, 7, 11, 14, 17, 20, 28, 39, 53, 65, 82, 107, 148, 196, 253, 319, 419, 558, 745, 964, 1244, 1615, 2141, 2825, 3698, 4787, 6244, 8196, 10805, 14135, 18427, 24014, 31489, 41332, 54172, 70711, 92357, 120849, 158482, 207547, 271412, 354628, 464045
Offset: 0

Views

Author

Roger L. Bagula, Mar 28 2005

Keywords

Comments

Set n=4, p=2, q=-1 and r=-1 in the characteristic polynomial x^n-p*x^(n-1)+q*x+r=0.

Crossrefs

Cf. A099206.

Programs

  • Mathematica
    CoefficientList[Series[(1+2x^3)/(1-x+x^3-2x^4),{x,0,50}],x] (* or *) LinearRecurrence[{1,0,-1,2},{1,1,1,2},50] (* Harvey P. Dale, Mar 30 2012 *)

Formula

a(n) = a(n-1) -a(n-3) +2*a(n-4).

Extensions

All values replaced consistent with the recurrence - the Assoc. Eds. of the OEIS - Jul 31 2010
Showing 1-3 of 3 results.