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 1-8 of 8 results.

A343097 Array read by antidiagonals: T(n,k) is the number of k-colorings of an n X n grid, up to rotations and reflections.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 1, 0, 1, 3, 6, 1, 0, 1, 4, 21, 102, 1, 0, 1, 5, 55, 2862, 8548, 1, 0, 1, 6, 120, 34960, 5398083, 4211744, 1, 0, 1, 7, 231, 252375, 537157696, 105918450471, 8590557312, 1, 0, 1, 8, 406, 1284066, 19076074375, 140738033618944, 18761832172500795, 70368882591744, 1, 0
Offset: 0

Views

Author

Andrew Howroyd, Apr 14 2021

Keywords

Examples

			Array begins:
====================================================================
n\k | 0 1       2            3               4                 5
----+---------------------------------------------------------------
  0 | 1 1       1            1               1                 1 ...
  1 | 0 1       2            3               4                 5 ...
  2 | 0 1       6           21              55               120 ...
  3 | 0 1     102         2862           34960            252375 ...
  4 | 0 1    8548      5398083       537157696       19076074375 ...
  5 | 0 1 4211744 105918450471 140738033618944 37252918396015625 ...
  ...
		

Crossrefs

Programs

  • PARI
    T(n,k) = {(k^(n^2) + 2*k^((n^2 + 3*(n%2))/4) + k^((n^2 + (n%2))/2) + 2*k^(n*(n+1)/2) + 2*k^(n*(n+n%2)/2) )/8}

Formula

T(n,k) = (k^(n^2) + 2*k^((n^2 + 3*(n mod 2))/4) + k^((n^2 + (n mod 2))/2) + 2*k^(n*(n+1)/2) + 2*k^(n*(n + n mod 2)/2) )/8.

A286392 Number of inequivalent n X n matrices over an alphabet of size 6 under action of dihedral group of the square D_4.

Original entry on oeis.org

1, 6, 231, 1284066, 352654485156, 3553786240466361696, 1289303099816839265917858176, 16839193280515921004090301582258640896, 7917535832871659713272867459049024690729209839616
Offset: 0

Views

Author

María Merino, Imanol Unanue, Yosu Yurramendi, May 08 2017

Keywords

Comments

Computed using Burnside's orbit-counting lemma.

Crossrefs

Column k=6 of A343097.

Programs

  • Mathematica
    Table[1/8*(6^(n^2) + 2*6^((n^2 + 3 #)/4) + (3 - 2 #)*6^((n^2 + #)/2) + (2 + 2 #)*6^((n^2 + n)/2)) &@ Boole[OddQ@ n], {n, 10}] (* Michael De Vlieger, May 08 2017 *)

Formula

a(n) = (1/8)*(6^(n^2) + 2*6^(n^2/4) + 3*6^(n^2/2) + 2*6^((n^2 + n)/2)) if n is even;
a(n) = (1/8)*(6^(n^2) + 2*6^((n^2 + 3)/4) + 6^((n^2 + 1)/2) + 4*6^((n^2 + n)/2)) if n is odd.

A286525 Number of inequivalent n X n matrices over GF(4) under action of dihedral group of the square D_4, with a fourth of 1's, 2's, 3's and 4's (ordered occurrences rounded up/down if n^2 != 0 mod 4).

Original entry on oeis.org

1, 1, 3, 978, 7885536, 1030690752000, 2681594035175055000, 111102459342780333711432912, 82765346051371433995689422809152600, 984929152509556378339959477248973638627262816, 201525938526971993585665495909682003042353826154218776128
Offset: 0

Views

Author

María Merino, Imanol Unanue, May 11 2017

Keywords

Examples

			For n=2 the a(2)=3 solutions are the colorings of 2 X 2 matrices in 4 colors inequivalent under the action of D_4 with exactly 1 occurrence of each color (coefficient of x1^1 x2^1 x3^1 x4^1).
		

Crossrefs

Formula

G.f.: g(x1,x2,x3,x4) = 1/8*(y1^(n^2) + 2*y1^n*y2^((n^2 - n)/2) + 3*y2^(n^2/2) + 2*y4^(n^2/4)) if n even and 1/8*(y1^(n^2) + 4*y1^n*y2^((n^2 - n)/2) + y1*y2^((n^2 - 1)/2) + 2*y1*y4^((n^2 - 1)/4)) if n odd, where coefficient correspond to y1 = x1 + x2 + x3 + x4, y2 = x1^2 + x2^2 + x3^2 + x4^2, y4 = x1^4 + x2^4 + x3^4 + x4^2 and occurrences of numbers are ceiling(n^2/4) for 1's and floor(n^2/4) for 2's, 3's and 4's.

A286393 Number of inequivalent n X n matrices over GF(7) under action of dihedral group of the square D_4.

Original entry on oeis.org

1, 7, 406, 5105212, 4154189102413, 167633579843887699759, 331466355732596931093508048522, 32115447190132359991237336502881651018804, 152470060954479462517322396167243320349298407119379801
Offset: 0

Views

Author

María Merino, Imanol Unanue, Yosu Yurramendi, May 08 2017

Keywords

Comments

Burnside's orbit-counting lemma

Crossrefs

Column k=7 of A343097.

Formula

a(n) = (1/8)*(7^(n^2) + 2*7^(n^2/4) + 3*7^(n^2/2) + 2*7^((n^2 + n)/2)) if n is even;
a(n) = (1/8)*(7^(n^2) + 2*7^((n^2 + 3)/4) + 7^((n^2 + 1)/2) + 4*7^((n^2 + n)/2)) if n is odd.

A286394 Number of inequivalent n X n matrices over GF(8) under action of dihedral group of the square D_4.

Original entry on oeis.org

1, 8, 666, 16912512, 35184646816768, 4722366500530551259136, 40564819207305653446303190876160, 22300745198530623151211847196048401987796992, 784637716923335095479473759060307277562325323313332617216
Offset: 0

Views

Author

María Merino, Imanol Unanue, Yosu Yurramendi, May 08 2017

Keywords

Comments

Burnside's orbit-counting lemma.

Crossrefs

Formula

a(n) = (1/8)*(8^(n^2) + 2*8^(n^2/4) + 3*8^(n^2/2) + 2*8^((n^2 + n)/2)) if n is even;
a(n) = (1/8)*(8^(n^2) + 2*8^((n^2 + 3)/4) + 8^((n^2 + 1)/2) + 4*8^((n^2 +n)/2)) if n is odd.

A047939 Number of 4-colorings of an n X n grid, up to rotational symmetry.

Original entry on oeis.org

1, 4, 70, 65824, 1073758336, 281474993496064, 1180591620734591303680, 79228162514264619068554215424, 85070591730234615870455337878516924416, 1461501637330902918203686041642102636484130504704, 401734511064747568885490523085607563280607806359022338048000
Offset: 0

Views

Author

Keywords

Crossrefs

Column k=4 of A343095.

Formula

a(n) = (m^(n^2) + 2 m^((n^2 + 3 (n mod 2))/4) + m^((n^2 + (n mod 2))/2))/4, with m = 4.

Extensions

Terms a(10) and beyond from Andrew Howroyd, Apr 14 2021

A286396 Number of inequivalent n X n matrices over GF(9) under action of dihedral group of the square D_4.

Original entry on oeis.org

1, 9, 1035, 48700845, 231628411446741, 89737248564744874067889, 2816049943117424212512789695666175, 7158021121277935153545945911617993395398302485, 1473773072217322896440109113309952350877179744639518847951721
Offset: 0

Views

Author

María Merino, Imanol Unanue, Yosu Yurramendi, May 08 2017

Keywords

Comments

Burnside's orbit-counting lemma.

Crossrefs

Programs

  • Mathematica
    Table[1/8*(9^(n^2) + 2*9^((n^2 + 3 #)/4) + (3 - 2 #)*9^((n^2 + #)/2) + (2 + 2 #)*9^((n^2 + n)/2)) &@ Boole@ OddQ@ n, {n, 0, 7}] (* Michael De Vlieger, May 12 2017 *)

Formula

a(n) = (1/8)*(9^(n^2) + 2*9^(n^2/4) + 3*9^(n^2/2) + 2*9^((n^2 + n)/2)) if n is even;
a(n) = (1/8)*(9^(n^2) + 2*9^((n^2 + 3)/4) + 9^((n^2 + 1)/2) + 4*9^((n^2 + n)/2)) if n is odd.

A286397 Number of inequivalent n X n matrices over an alphabet of size 10 under action of dihedral group of the square D_4.

Original entry on oeis.org

1, 10, 1540, 125512750, 1250002537502500, 1250000000501250002500000, 125000000000000250375000000250000000, 1250000000000000000005001250000000002500000000000
Offset: 0

Views

Author

María Merino, Imanol Unanue, Yosu Yurramendi, May 08 2017

Keywords

Comments

Burnside's orbit-counting lemma.

Crossrefs

Programs

  • Mathematica
    Table[1/8*(10^(n^2) + 2*10^((n^2 + 3 #)/4) + (3 - 2 #)*10^((n^2 + #)/2) + (2 + 2 #)*10^((n^2 + n)/2)) &@ Boole@ OddQ@ n, {n, 7}] (* Michael De Vlieger, May 12 2017 *)

Formula

a(n) = (1/8)*(10^(n^2) + 2*10^(n^2/4) + 3*10^(n^2/2) + 2*10^((n^2 + n)/2)) if n is even;
a(n) = (1/8)*(10^(n^2) + 2*10^((n^2 + 3)/4) + 10^((n^2 + 1)/2) + 4*10^((n^2 + n)/2)) if n is odd.
Showing 1-8 of 8 results.