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.

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A300068 A sequence based on the period 6 sequence A300067.

Original entry on oeis.org

0, 0, 0, 1, 2, 2, 3, 3, 3, 4, 5, 5, 6, 6, 6, 7, 8, 8, 9, 9, 9, 10, 11, 11, 12, 12, 12, 13, 14, 14, 15, 15, 15, 16, 17, 17, 18, 18, 18, 19, 20, 20, 21, 21, 21, 22, 23, 23, 24, 24, 24, 25, 26, 26, 27, 27, 27, 28, 29, 29, 30, 30, 30, 31, 32, 32, 33, 33, 33, 34, 35, 35, 36, 36, 36, 37, 38, 38, 39, 39, 39, 40, 41, 41
Offset: 0

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Author

Wolfdieter Lang, Feb 24 2018

Keywords

Comments

From Wolfdieter Lang, Mar 30 2018: (Start)
a(k) + 2 =: s(k) is used to obtain for 2^s(k)*vec v_{-k} integer components in the quadratic number field Q(sqrt(3)), where vec v_{-k} = vec(O_{-(k+1)}, O_{-k})) with the centers O_{-k}, k >= 0, for a k-family of regular hexagons H_{-k} forming part of a discrete spiral. See the linked paper, Lemma 4 and Table 7.
a(k+2) =: v0(k), k >= 0, based on the sequence A300290, is used to obtain for
2^(v0(k))*V_{-k}(0) as well as 2^(v0(k))*V_{-k}(3) integer coordinates in the quadratic number field Q(sqrt(3)), where V_{-k}(j), j = 0..5, are the vertices of the regular hexagon H_{-k}, of the above mentioned k-family. See the linked paper, Lemma 6 and Table 8.
a(k+1) + 1 =: v1(k), k >= 1, is used to obtain for 2^(v1(k))*V_{-k}(1) as well as 2^(v1(k))*V_{-k}(4) integer coordinates in the quadratic number field Q(sqrt(3)), with vertices V_{-k}(j) of H_{-k}. See the linked paper, Lemma 6 and Table 9.
(End)

Crossrefs

Programs

  • Maple
    ListTools:-PartialSums(map(op, [[0],[0, 0, 1, 1, 0, 1]$30])); # Robert Israel, Mar 25 2018
  • Mathematica
    CoefficientList[Series[x^3*(1 + x + x^3)/((1 - x^6) (1 - x)), {x, 0, 102}], x] (* or *)
    MapIndexed[#1 + 3 Floor[(First[#2] - 1)/6] &, PadRight[{}, 102, {0, 0, 0, 1, 2, 2}]] (* Michael De Vlieger, Feb 25 2018 *)
  • PARI
    a300067(n) = my(v=[0, 0, 1, 2, 2]); v[if(n%6==0, 1, n%6)]
    a(n) = a300067(n) + 3*floor(n/6) \\ Felix Fröhlich, Feb 24 2018
    
  • PARI
    concat([0, 0, 0], Vec(x^3*(1 + x + x^3)/((1 - x^6)*(1 - x)) + O(x^40))) \\ Felix Fröhlich, Feb 24 2018

Formula

a(n) = A300067(n) + 3*floor(n/6), n >= 0.
G.f.: x^3*(1 + x + x^3)/((1 - x^6)*(1 - x)).
a(n+2) = A300290(n) + 3*floor(n/6), n >= 0.
a(n) = (6*n - 5 + cos(n*Pi) + 4*cos((n+1)*Pi/3) - 4*cos(2*(n+1)*Pi/3))/12. - Wesley Ivan Hurt, Oct 04 2018
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