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.

A103997 Square array T(M,N) read by antidiagonals: number of dimer tilings of a 2*M X 2*N Moebius strip.

Original entry on oeis.org

1, 1, 1, 1, 3, 1, 1, 11, 7, 1, 1, 41, 71, 18, 1, 1, 153, 769, 539, 47, 1, 1, 571, 8449, 17753, 4271, 123, 1, 1, 2131, 93127, 603126, 434657, 34276, 322, 1, 1, 7953, 1027207, 20721019, 46069729, 10894561, 276119, 843, 1, 1, 29681, 11332097, 714790675, 4974089647, 3625549353, 275770321, 2226851, 2207, 1
Offset: 0

Views

Author

Ralf Stephan, Feb 26 2005

Keywords

Examples

			Array begins:
  1,   1,     1,        1,          1,             1,               1,
  1,   3,     7,       18,         47,           123,             322,
  1,  11,    71,      539,       4271,         34276,          276119,
  1,  41,   769,    17753,     434657,      10894561,       275770321,
  1, 153,  8449,   603126,   46069729,    3625549353,    289625349454,
  1, 571, 93127, 20721019, 4974089647, 1234496016491, 312007855309063,
  ...
		

Crossrefs

Rows include A005248, A103998.
Columns 1..7 give A001835(n+1), A334135, A334179, A334180, A334181, A334182, A334183.
Main diagonal gives A334124.

Programs

  • Mathematica
    T[M_, N_] := Product[4Sin[(4n-1)Pi/(4N)]^2 + 4Cos[m Pi/(2M+1)]^2, {n, 1, N}, {m, 1, M}];
    Table[T[M - N, N] // Round, {M, 0, 9}, {N, 0, M}] // Flatten (* Jean-François Alcover, Dec 03 2018 *)

Formula

T(M, N) = Product_{m=1..M} (Product_{n=1..N} 4*sin(Pi*(4*n-1)/(4*N))^2 + 4*cos(Pi*m/(2*M + 1))^2).
For k > 0, T(n,k) = 2^n * sqrt(Resultant(U_{2*n}(x/2), T_{2*k}(i*x/2))), where T_n(x) is a Chebyshev polynomial of the first kind, U_n(x) is a Chebyshev polynomial of the second kind and i = sqrt(-1). - Seiichi Manyama, Apr 15 2020

A334179 Number of dimer tilings of a 2*n x 6 Moebius strip.

Original entry on oeis.org

1, 18, 539, 17753, 603126, 20721019, 714790675, 24693540102, 853526336417, 29507528240963, 1020183543633762, 35272351950083641, 1219535200106522761, 42165342386915661378, 1457865351514568764211, 50405667966576581717969, 1742775306265709714234214, 60256436430143085819341347
Offset: 0

Views

Author

Seiichi Manyama, Apr 17 2020

Keywords

Crossrefs

Column 3 of A103997.
Column 6 of A334178.

Programs

  • Mathematica
    a[n_] := 2^n * Sqrt[Resultant[ChebyshevU[2*n, x/2], ChebyshevT[6, I*x/2], x]]; Array[a, 18, 0] (* Amiram Eldar, May 04 2021 *)
  • PARI
    {a(n) = sqrtint(4^n*polresultant(polchebyshev(2*n, 2, x/2), polchebyshev(6, 1, I*x/2)))}

Formula

a(n)^2 = 4^n * Resultant(U_{2*n}(x/2), T_{6}(i*x/2)), where T_n(x) is a Chebyshev polynomial of the first kind, U_n(x) is a Chebyshev polynomial of the second kind and i = sqrt(-1).

A334180 Number of dimer tilings of a 2*n x 8 Moebius strip.

Original entry on oeis.org

1, 47, 4271, 434657, 46069729, 4974089647, 541714928431, 59235304882177, 6489376893239297, 711542422708907311, 78049793235712789423, 8562932336475599244257, 939528644055272842890721, 103089508033934831216777903, 11311669427350891385087911471
Offset: 0

Views

Author

Seiichi Manyama, Apr 17 2020

Keywords

Crossrefs

Column 4 of A103997.
Column 8 of A334178.

Programs

  • Mathematica
    a[n_] := 2^n * Sqrt[Resultant[ChebyshevU[2*n, x/2], ChebyshevT[8, I*x/2], x]]; Array[a, 15, 0] (* Amiram Eldar, May 04 2021 *)
  • PARI
    {a(n) = sqrtint(4^n*polresultant(polchebyshev(2*n, 2, x/2), polchebyshev(8, 1, I*x/2)))}

Formula

a(n)^2 = 4^n * Resultant(U_{2*n}(x/2), T_{8}(i*x/2)), where T_n(x) is a Chebyshev polynomial of the first kind, U_n(x) is a Chebyshev polynomial of the second kind and i = sqrt(-1).

A334181 Number of dimer tilings of a 2*n x 10 Moebius strip.

Original entry on oeis.org

1, 123, 34276, 10894561, 3625549353, 1234496016491, 425588878897051, 147716667776449068, 51459452422736225401, 17962375573820654607091, 6276640725138515237851803, 2194525820018749279915303361, 767517569389298359121889024076, 268477550040900162034429991254323
Offset: 0

Views

Author

Seiichi Manyama, Apr 17 2020

Keywords

Crossrefs

Column 5 of A103997.
Column 10 of A334178.

Programs

  • Mathematica
    a[n_] := 2^n * Sqrt[Resultant[ChebyshevU[2*n, x/2], ChebyshevT[10, I*x/2], x]]; Array[a, 14, 0] (* Amiram Eldar, May 04 2021 *)
  • PARI
    {a(n) = sqrtint(4^n*polresultant(polchebyshev(2*n, 2, x/2), polchebyshev(10, 1, I*x/2)))}

Formula

a(n)^2 = 4^n * Resultant(U_{2*n}(x/2), T_{10}(i*x/2)), where T_n(x) is a Chebyshev polynomial of the first kind, U_n(x) is a Chebyshev polynomial of the second kind and i = sqrt(-1).

A334182 Number of dimer tilings of a 2*n x 12 Moebius strip.

Original entry on oeis.org

1, 322, 276119, 275770321, 289625349454, 312007855309063, 341133743251787719, 376320092633385077198, 417378876015895466713681, 464421220758849403137304663, 517771128105959394949223994178, 577920313480485996169789045855489, 645503767039127463811947619425652481
Offset: 0

Views

Author

Seiichi Manyama, Apr 17 2020

Keywords

Crossrefs

Column 6 of A103997.
Column 12 of A334178.

Programs

  • Mathematica
    a[n_] := 2^n * Sqrt[Resultant[ChebyshevU[2*n, x/2], ChebyshevT[12, I*x/2], x]]; Array[a, 13, 0] (* Amiram Eldar, May 04 2021 *)
  • PARI
    {a(n) = sqrtint(4^n*polresultant(polchebyshev(2*n, 2, x/2), polchebyshev(12, 1, I*x/2)))}

Formula

a(n)^2 = 4^n * Resultant(U_{2*n}(x/2), T_{12}(i*x/2)), where T_n(x) is a Chebyshev polynomial of the first kind, U_n(x) is a Chebyshev polynomial of the second kind and i = sqrt(-1).

A334183 Number of dimer tilings of a 2*n x 14 Moebius strip.

Original entry on oeis.org

1, 843, 2226851, 7009284232, 23313951730593, 79684937704014787, 276820366633357961907, 971684488369988888850993, 3433809783046699326165318697, 12187832583695135440208385490411, 43381711462091769247169214041784216, 154696550169813236996441805153918153313
Offset: 0

Views

Author

Seiichi Manyama, Apr 17 2020

Keywords

Crossrefs

Column 7 of A103997.
Column 14 of A334178.

Programs

  • Mathematica
    a[n_] := 2^n * Sqrt[Resultant[ChebyshevU[2*n, x/2], ChebyshevT[14, I*x/2], x]]; Array[a, 12, 0] (* Amiram Eldar, May 04 2021 *)
  • PARI
    {a(n) = sqrtint(4^n*polresultant(polchebyshev(2*n, 2, x/2), polchebyshev(14, 1, I*x/2)))}

Formula

a(n)^2 = 4^n * Resultant(U_{2*n}(x/2), T_{14}(i*x/2)), where T_n(x) is a Chebyshev polynomial of the first kind, U_n(x) is a Chebyshev polynomial of the second kind and i = sqrt(-1).
Showing 1-6 of 6 results.