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 1-5 of 5 results.

A233320 Number A(n,k) of tilings of a k X n rectangle using trominoes of any shape; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0, 3, 3, 0, 1, 1, 0, 0, 10, 0, 0, 1, 1, 1, 0, 23, 23, 0, 1, 1, 1, 0, 11, 62, 0, 62, 11, 0, 1, 1, 0, 0, 170, 0, 0, 170, 0, 0, 1, 1, 1, 0, 441, 939, 0, 939, 441, 0, 1, 1, 1, 0, 41, 1173, 0, 8342, 8342, 0, 1173, 41, 0, 1
Offset: 0

Views

Author

Alois P. Heinz, Dec 07 2013

Keywords

Comments

Every row and column satisfies a linear recurrence. - Peter Kagey, Jul 17 2019

Examples

			Square array A(n,k) begins:
  1, 1,  1,    1,   1,    1,       1, ...
  1, 0,  0,    1,   0,    0,       1, ...
  1, 0,  0,    3,   0,    0,      11, ...
  1, 1,  3,   10,  23,   62,     170, ...
  1, 0,  0,   23,   0,    0,     939, ...
  1, 0,  0,   62,   0,    0,    8342, ...
  1, 1, 11,  170, 939, 8342,   80092, ...
  1, 0,  0,  441,   0,    0,  614581, ...
  1, 0,  0, 1173,   0,    0, 5271923, ...
		

Crossrefs

Formula

A(n,k) = 0 <=> n*k mod 3 > 0.

A134438 Number of tilings of a 3 X n rectangle with n trominoes.

Original entry on oeis.org

1, 1, 3, 10, 23, 62, 170, 441, 1173, 3127, 8266, 21937, 58234, 154390, 409573, 1086567, 2882021, 7645046, 20279829, 53794224, 142696606, 378522507, 1004078871, 2663452699, 7065162260, 18741269167, 49713692146, 131872134232, 349808216915, 927912454723
Offset: 0

Views

Author

Philippe Deléham, Jan 18 2008

Keywords

References

  • G. Kreweras, Recouvrements d'un rectangle de largeur 3 à l'aide de triminos, Mathématiques et sciences humaines, tome 130 (1995), p. 27-31.

Crossrefs

Programs

  • Maple
    a:= n-> (Matrix([[1$2, 0$2, 1, 0]]). Matrix(6, (i,j)-> if i+1=j then 1 elif j=1 then [1, 2, 6, 1, 0, -1][i] else 0 fi)^n)[1,2]: seq(a(n), n=0..30);  # Alois P. Heinz, Oct 09 2008
  • Mathematica
    LinearRecurrence[{1,2,6,1,0,-1},{1,1,3,10,23,62},40] (* Harvey P. Dale, Aug 27 2013 *)

Formula

a(n) = a(n-1) +2*a(n-2) +6*a(n-3) +a(n-4) -a(n-6).
G.f.: (1-x^3) / (1-x-2*x^2-6*x^3-x^4+x^6). - Alois P. Heinz, Oct 09 2008

Extensions

More terms from Alois P. Heinz, Oct 09 2008

A233290 Number of tilings of a 6 X n rectangle with 2n trominoes of any shape.

Original entry on oeis.org

1, 1, 11, 170, 939, 8342, 80092, 614581, 5271923, 45832761, 379419508, 3223419241, 27438555522, 231096250072, 1958024834151, 16593169804557, 140295718998907, 1187830239559588, 10056816580083721, 85104482994177208, 720410915948382970, 6098207777286812381
Offset: 0

Views

Author

Alois P. Heinz, Dec 06 2013

Keywords

Examples

			a(2) = 11:
.___. .___. .___. .___. .___. .___. .___. .___. .___. .___. .___.
| | | | ._| |_. | | ._| | | | |_. | | | | |_. | | ._| | ._| |_. |
| | | |_| | | |_| |_| | | | | | |_| | | | | |_| |_| | |_| | | |_|
|_|_| |___| |___| |___| |_|_| |___| |_|_| |___| |___| | | | | | |
| | | | ._| |_. | | | | | ._| | | | |_. | | ._| |_. | | |_| |_| |
| | | |_| | | |_| | | | |_| | | | | | |_| |_| | | |_| |_| | | |_|
|_|_| |___| |___| |_|_| |___| |_|_| |___| |___| |___| |___| |___|.
		

Crossrefs

Column k=6 of A233320.

A269664 Number of tilings of a 12 X n rectangle with 4n trominoes of any shape.

Original entry on oeis.org

1, 1, 153, 58234, 1895145, 198253934, 27438555522, 1949314526229, 193553900967497, 20574308184277971, 1830607857363940042, 178792253082742021463, 17735061025562799941630, 1679378707647721857218932, 163105210594579645492072521, 15894545877032388610890500803
Offset: 0

Views

Author

Alois P. Heinz, Mar 02 2016

Keywords

Crossrefs

Column k=12 of A233320.

A215827 Number of intermediate configurations needed to be stored to calculate the number of ways in which a 9 X n grid can be tiled with triominoes.

Original entry on oeis.org

4, 360, 4261, 20104, 44654, 70166, 95681, 121196, 146711, 172226, 197741, 223256, 248771, 274286, 299801, 325316, 350831, 376346, 401861, 427376, 452891, 478406, 503921, 529436, 554951, 580466, 605981, 631496, 657011, 682526, 708041, 733556, 759071, 784586
Offset: 1

Views

Author

V. Raman, Aug 23 2012

Keywords

Comments

a(n+1) - a(n) = 25515, for all n >= 6.

Crossrefs

Cf. A215826 (Number of ways in which a 9 X n grid can be tiled with triominoes).

Extensions

Definition corrected by V. Raman, Oct 22 2012
a(1) inserted and more terms a(23)-a(34) from V. Raman, Oct 24 2012
Showing 1-5 of 5 results.