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.

A136775 Number of multiplex juggling sequences of length n, base state <1,1> and hand capacity 2.

Original entry on oeis.org

1, 3, 11, 40, 145, 525, 1900, 6875, 24875, 90000, 325625, 1178125, 4262500, 15421875, 55796875, 201875000, 730390625, 2642578125, 9560937500, 34591796875, 125154296875, 452812500000, 1638291015625, 5927392578125, 21445507812500, 77590576171875
Offset: 1

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Author

Steve Butler, Jan 21 2008

Keywords

Comments

Except for the initial 1, this is the p-INVERT of (1,1,1,1,1,...) for p(S) = 1 - 3 S + S^2; see A291000. - Clark Kimberling, Aug 24 2017

Crossrefs

Cf. A136776.

Programs

  • Magma
    R:=PowerSeriesRing(Integers(), 27); Coefficients(R!( (x-2*x^2+x^3)/(1-5*x+5*x^2))); // Marius A. Burtea, Jan 13 2020
  • Mathematica
    CoefficientList[Series[(x^2-2x+1)/(5x^2-5x+1),{x,0,30}],x] (* Harvey P. Dale, Jun 22 2014 *)
  • PARI
    Vec((x-2*x^2+x^3)/(1-5*x+5*x^2) + O(x^30)) \\ Colin Barker, Aug 31 2016
    

Formula

G.f.: (x-2x^2+x^3)/(1-5x+5x^2).
a(n) = 5*a(n-1)-5*a(n-2) for n>3. - Colin Barker, Aug 31 2016

A322504 a(n) = -4*a(n-1) - 3*a(n-2) + a(n-3), a(0) = 1, a(1) = -2, a(2) = 4.

Original entry on oeis.org

1, -2, 4, -9, 22, -57, 153, -419, 1160, -3230, 9021, -25234, 70643, -197849, 554233, -1552742, 4350420, -12189221, 34152882, -95693445, 268125913, -751270435, 2105010556, -5898105006, 16526117921, -46305146110, 129744125671, -363534946433, 1018602262609, -2854060085466, 7996898607604
Offset: 0

Views

Author

Kai Wang, Jan 10 2019

Keywords

Comments

Let {X,Y,Z} be the roots of the cubic equation t^3 + at^2 + bt + c = 0 where {a, b, c} are integers.
Let {u, v, w} be three numbers such that {u + v + w, u*X + v*Y + w*Z, u*X^2 + v*Y^2 + w*Z^2} are integers.
Then {p(n) = u*X^n + v*Y^n + w*Z^n | n = 0, 1, 2, ...} is an integer sequence with the recurrence relation: p(n) = -a*p(n-1) - b*p(n-2) - c*p(n-3).
Let k = Pi/7.
This sequence has (a, b, c) = (4, 3, -1), (u, v, w) = (1/(sqrt(7)*tan(8k)), 1/(sqrt(7)*tan(2k)), 1/(sqrt(7)*tan(4k))).
A215404: (a, b, c) = (4, 3, -1), (u, v, w) = (1/(sqrt(7)*tan(2k)), 1/(sqrt(7)*tan(4k)), 1/(sqrt(7)*tan(8k))).
A136776: (a, b, c) = (4, 3, -1), (u, v, w) = (1/(sqrt(7)*tan(4k)), 1/(sqrt(7)*tan(8k)), 1/(sqrt(7)*tan(2k))).
X = (sin(2k)*sin(2k))/(sin(4k)*sin(8k)), Y = (sin(4k)*sin(4k))/(sin(8k)*sin(2k)), Z = (sin(8k)*sin(8k))/(sin(2k)*sin(4k)).

Crossrefs

Programs

  • Magma
    I:=[1,-2,4]; [n le 3 select I[n] else -4*Self(n-1) - 3*Self(n-2) + Self(n-3): n in [1..31]]; // Vincenzo Librandi, Jan 13 2019
  • Mathematica
    LinearRecurrence[{-4,-3,1},{1,-2,4},50] (* Stefano Spezia, Jan 11 2019 *)
    RecurrenceTable[{a[0]==1, a[1]==-2, a[2]==4, a[n]==-4 a[n-1]-3 a[n-2]+a[n-3]}, a, {n, 30}] (* Vincenzo Librandi, Jan 13 2019 *)
  • PARI
    Vec((1 + 2*x - x^2) / (1 + 4*x + 3*x^2 - x^3) + O(x^30)) \\ Colin Barker, Jan 11 2019
    

Formula

G.f.: (1 + 2*x - x^2) / (1 + 4*x + 3*x^2 - x^3). - Colin Barker, Jan 11 2019
Showing 1-2 of 2 results.