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.

A351322 Number T(n,k) of tilings of a 3k X n rectangle with right trominoes.

Original entry on oeis.org

1, 1, 1, 1, 0, 1, 1, 0, 2, 1, 1, 0, 4, 0, 1, 1, 0, 8, 8, 4, 1, 1, 0, 16, 0, 18, 0, 1, 1, 0, 32, 64, 88, 72, 8, 1, 1, 0, 64, 0, 468, 384, 162, 0, 1, 1, 0, 128, 512, 2672, 8544, 4312, 520, 16, 1, 1, 0, 256, 0, 16072, 76800, 118586, 22656, 1514, 0, 1, 1, 0, 512, 4096, 100064, 1168512, 3403624, 1795360, 204184, 4312, 32, 1
Offset: 0

Views

Author

Gerhard Kirchner, Feb 21 2022

Keywords

Comments

The table is read by descending antidiagonals.
If read by columns or rows:
T(n,1) = A077957(n+1)
T(2,k) = A000079(k) = 2^k
T(4,k) = A046984(k)
T(5,k) = A084478(k)
T(n,2) = A351323(n)
T(7,k) = A351324(k)
Linear recurrences with different numbers of parameters are known for the sequences above.
Overview:
Constant Number of
side length Sequence parameters
2 T(2,k) 1
3 T(n,1),T(3,k) 2
4 T(4,k) 3 see A046984
5 T(5,k) 4 see A084478
6 T(n,2),T(6,k) 11 see A351323
7 T(7,k) 17 see A351324
8 T(8,k) >30
9 T(n,3),T(9,k) >30

Examples

			6 X 2 rectangle: 4 tilings
   ___   ___   ___   ___
  |  _| |  _| |_  | |_  |
  |_| | |_| | | |_| | |_|
  |___| |___| |___| |___|
  |  _| |_  | |  _| |_  |
  |_| | | |_| |_| | | |_|
  |___| |___| |___| |___|
.
Table T(n,k) begins:
  n\k__0__1______2_________3_____________4
   0:  1  1      1         1             1
   1:  1  0      0         0             0
   2:  1  2      4         8            16
   3:  1  0      8         0            64
   4:  1  4     18        88           468
   5:  1  0     72       384          8544
   6:  1  8    162      4312        118586
   7:  1  0    520     22656       1795360
   8:  1 16   1514    204184      29986082
   9:  1  0   4312   1193600     467966840
  10:  1 32  13242   9567192    7758809670
  11:  1  0  39088  63112256  124693887784
		

Crossrefs

Programs

  • Maxima
    See Maxima Code link.

A084480 Number of tilings of a 4 X 2n rectangle with L tetrominoes.

Original entry on oeis.org

1, 2, 10, 42, 182, 790, 3432, 14914, 64814, 281680, 1224182, 5320310, 23122148, 100489226, 436727814, 1898026232, 8248853134, 35849651070, 155803171860, 677123141810, 2942788286798, 12789406189672, 55582969192486, 241564496305670, 1049843265359828
Offset: 0

Views

Author

Ralf Stephan, May 27 2003

Keywords

Crossrefs

Programs

  • Mathematica
    LinearRecurrence[{4, 2, -1, -4, -4, -2}, {1, 2, 10, 42, 182, 790}, 25] (* Jean-François Alcover, Feb 25 2020 *)
  • PARI
    Vec((1 - 2*x - x^3) / (1 - 4*x - 2*x^2 + x^3 + 4*x^4 + 4*x^5 + 2*x^6) + O(x^30)) \\ Colin Barker, Mar 28 2017

Formula

G.f.: (1-2*z-z^3) / (1-4*z-2*z^2+z^3+4*z^4+4*z^5+2*z^6).
a(n) = 4*a(n-1) + 2*a(n-2) - a(n-3) - 4*a(n-4) - 4*a(n-5) - 2*a(n-6) for n>5. - Colin Barker, Mar 28 2017

Extensions

Inserted a(0)=1 by Alois P. Heinz, May 01 2013

A084477 Number of fault-free tilings of a 4 X 3n rectangle with right trominoes.

Original entry on oeis.org

4, 2, 8, 48, 288, 1728, 10368, 62208, 373248, 2239488, 13436928, 80621568, 483729408, 2902376448, 17414258688, 104485552128, 626913312768, 3761479876608, 22568879259648, 135413275557888, 812479653347328, 4874877920083968, 29249267520503808
Offset: 1

Views

Author

Ralf Stephan, May 27 2003

Keywords

Comments

A tromino is a 3-celled L-shaped piece (a 2 X 2 square with one of the four cells omitted). - N. J. A. Sloane, Mar 28 2017
Fault-free tilings are those where the only straight interface is at the left and right end. Thus a(n) <= A046984(n).

Crossrefs

Programs

  • PARI
    Vec(2*x*(2 - 11*x - 2*x^2) / (1 - 6*x) + O(x^30)) \\ Colin Barker, Mar 28 2017

Formula

a(n) = 2*A067411(n-2) for n>1.
G.f.: 2*z(2-11*z-2*z^2) / (1-6*z).
a(n) = 8 * 6^(n-3) for n>2.
G.f.: 9/2 - x - 1/Q(0) where Q(k)= 1 + 5^k/(1 - 2*x/(2*x + 5^k/Q(k+1) )); (continued fraction ). - Sergei N. Gladkovskii, Apr 10 2013
a(n) = 6*a(n-1) for n>2. - Colin Barker, Mar 28 2017

A046984 Number of ways to tile a 4 X 3n rectangle with right trominoes.

Original entry on oeis.org

1, 4, 18, 88, 468, 2672, 16072, 100064, 636368, 4097984, 26579488, 173093760, 1129796928, 7383588608, 48287978624, 315921649152, 2067346607360, 13530037877760, 88555066819072, 579620448450560, 3793872862974976, 24832858496561152, 162544900186359808
Offset: 0

Views

Author

Cristopher Moore (moore(AT)santafe.edu)

Keywords

Comments

The sequence of tiling 2 X 3n rectangles with L-trominoes is 2^n. The sequence of tiling 3 X 2n rectangles is 2^n. All these tilings have vertical faults but no horizontal faults. - R. J. Mathar, Dec 08 2022
This sequence is the Hadamard sum of the following 4 sequences: 0, 0, 16, 64, 256, 1024, 4096... (A000302, tilings which have both vertical and horizontal faults), 0, 4, 0, 0, 0, 0, 0, ...(tilings which have horizontal but no vertical faults), 0, 0, 0, 16, 164, 1360, 10248, 73312, 508624, 3462592, 23291424.. (tilings which have vertical but no horizontal faults), 1, 0, 2, 8, 48, 288, 1728, 10368,.. (essentially A084477, tilings which have neither vertical nor horizontal faults). - R. J. Mathar, Dec 08 2022

References

  • Suggested on p. 96 of 1994 edition of "Polyominoes" by Samuel W. Golomb.

Crossrefs

Cf. A084478 (5 X 3n), A351323 (6 X n), A351324 (7 X 3n), A049086 (straight trominoes), A233339 (mixed trominoes).

Programs

  • Maple
    a:= n-> (<<0|1|0>, <0|0|1>, <-4|-22|10>>^n. <<1, 4, 18>>)[1, 1]:
    seq(a(n), n=0..22);  # Alois P. Heinz, Feb 21 2022
  • Mathematica
    CoefficientList[Series[(1-6x)/(1-10x+22x^2+4x^3),{x,0,40}],x] (* or *) LinearRecurrence[{10,-22,-4},{1,4,18},40] (* Harvey P. Dale, Mar 31 2012 *)
  • PARI
    a(n)=([0,1,0; 0,0,1; -4,-22,10]^n*[1;4;18])[1,1] \\ Charles R Greathouse IV, Feb 10 2017

Formula

G.f.: (1 - 6*x)/(1 - 10*x + 22*x^2 + 4*x^3).
a(0)=1, a(1)=4, a(2)=18, a(n)=10*a(n-1)-22*a(n-2)-4*a(n-3). - Harvey P. Dale, Mar 31 2012

A084479 Number of fault-free tilings of a 5 X 3n rectangle with right trominoes.

Original entry on oeis.org

72, 384, 3360, 21504, 163968, 1136640, 8283648, 58791936, 423121920, 3022872576, 21679875072, 155169515520, 1111792499712, 7961492434944, 57028930483200, 408439216748544, 2925470825868288, 20952944438968320, 150073631759459328, 1074876158496638976
Offset: 2

Views

Author

Ralf Stephan, May 27 2003

Keywords

Comments

A tromino is a 3-celled L-shaped piece (a 2 X 2 square with one of the four cells omitted). - N. J. A. Sloane, Mar 28 2017
Fault-free tilings are those where the only straight interface is at the left and right end. Thus a(n) <= A084478(n).

Crossrefs

Programs

  • Mathematica
    LinearRecurrence[{2, 31, 40, 20}, {72, 384, 3360, 21504}, 20] (* Jean-François Alcover, Jan 07 2019 *)
  • PARI
    Vec(24*x^2*(3 + 10*x + 15*x^2) / (1 - 2*x - 31*x^2 - 40*x^3 - 20*x^4) + O(x^30)) \\ Colin Barker, Mar 28 2017

Formula

G.f.: 24*z^2*(3 + 10*z + 15*z^2) / (1 - 2*z - 31*z^2 - 40*z^3 - 20*z^4).
a(n) = 2*a(n-1) + 31*a(n-2) + 40*a(n-3) + 20*a(n-4) for n > 5. - Colin Barker, Mar 28 2017

A084481 Number of fault-free tilings of a 4 X 2n rectangle with L tetrominoes.

Original entry on oeis.org

2, 6, 10, 18, 38, 84, 186, 410, 904, 1994, 4398, 9700, 21394, 47186, 104072, 229538, 506262, 1116596, 2462730, 5431722, 11980040, 26422810, 58277342, 128534724, 283492258, 625261858, 1379058440, 3041609138, 6708480134, 14796018708, 32633646554, 71975773242
Offset: 1

Views

Author

Ralf Stephan, May 27 2003

Keywords

Comments

Fault-free tilings are those where the only straight interface is at the left and right end. Thus a(n) <= A084480(n).
If the conjectured G.F. in A183304 is true, then a(n)= 2*A183304(n-1), n>3. - R. J. Mathar, Dec 02 2022

Crossrefs

Programs

  • PARI
    Vec(2*x*(1 + x)^2*(1 - x - x^3) / (1 - 2*x - x^3) + O(x^30)) \\ Colin Barker, Mar 28 2017

Formula

G.f.: 2*z*(1+z)^2*(1-z-z^3) / (1-2*z-z^3).
a(n) = 2*a(n-1) + a(n-3) for n>6. - Colin Barker, Mar 28 2017

A351323 Number of tilings of a 6 X n rectangle with right trominoes.

Original entry on oeis.org

1, 0, 4, 8, 18, 72, 162, 520, 1514, 4312, 13242, 39088, 118586, 361712, 1103946, 3403624, 10513130, 32614696, 101530170, 316770752, 990771834, 3104283168, 9741133578, 30606719000, 96263812906, 303028237848, 954563802106, 3008665176560, 9487377712634, 29928407213328
Offset: 0

Views

Author

Gerhard Kirchner, Feb 21 2022

Keywords

Comments

See A351322 for algorithm. The subsequence 1,8,162,... for 6 X 3n rectangles also has a depending recurrence with 11 parameters.
The sequence is the Hadamard sum of the following 4 sequences: 0, 0, 0, 0, 16, 0, 128, 0, 256, 768, 1024,0, 13440, 0, 16384, .. (tilings which have both horizontal and vertical faults), 0, 0, 4, 8, 0, 0, 16, 0, 0, 128, 0, 0, 1536, 0, 0,.. (tilings which have horizontal faults but no vertical faults), 0, 0, 0, 0, 0, 64, 16, 480, 1140, 3200, 11208, 36032, 95924, 333856, 1003096,.. (tilings which have vertical faults but no horizontal faults), 1, 0, 0, 0, 2, 8, 2, 40, 118, 216, 1010, 3056, 7686, 27856, 84466,... (tilings which have neither vertical nor horizontal faults). - R. J. Mathar, Dec 08 2022

Examples

			For a 6 X 2 rectangle there are 4 tilings:
   ___   ___   ___   ___
  |  _| |  _| |_  | |_  |
  |_| | |_| | | |_| | |_|
  |___| |___| |___| |___|
  |  _| |_  | |  _| |_  |
  |_| | | |_| |_| | | |_|
  |___| |___| |___| |___|
		

Crossrefs

Cf. A077957, A000079, A046984, A084478, A351322, A351324, A236576 (straight trominoes), A233290 (mixed trominoes).

Formula

G.f.: (1 - x)*(1 - x - 5*x^2 - 7*x^3 + 6*x^4 + 12*x^5 + 6*x^6)/(1 - 2*x - 8*x^2 - 2*x^3 + 43*x^4 + 42*x^5 - 36*x^6 - 102*x^7 + 44*x^9 + 8*x^10 + 8*x^11).
a(n) = Sum_{i=0..10} b(i)*a(n-11+i) for n>10 where {b(i)} = {-8,-8,-44,0,102,36,-42,-43,2,8,2}.

A351324 Number of tilings of a 7 X 3n rectangle with right trominoes.

Original entry on oeis.org

1, 0, 520, 22656, 1795360, 115363072, 7876120608, 527256809600, 35522814546496, 2388257605782016, 160678147466414272, 10807663334085120512, 727010169682181839360, 48903265220016072792320, 3289569236212332037229184, 221278350342281369716796672
Offset: 0

Views

Author

Gerhard Kirchner, Feb 21 2022

Keywords

Comments

See A351322 for algorithm.
This is the Hadamard sum of the following 4 sequences: 0, 0,0,0, 158208,.. (tilings which have both vertical and horizontal faults), 0,0,480,6144, 125952 ... (tilings which have horizontal faults but no vertical faults), 00,0,0,112192,.. (tilings which have vertical but no horizontal faults), 1, 0,40, 16512, 1399008 ,... (tilings which have neither horizontal nor vertical faults). - R. J. Mathar, Dec 08 2022

Crossrefs

Cf. A077957, A000079, A046984, A084478, A351322, A351323, A236578 (straight trominoes), A233343 (mixed trominoes).

Formula

G.f.: (1 - 22*x - 1831*x^2 - 29454*x^3 - 270630*x^4 - 2070388*x^5 - 12125943*x^6 - 48147976*x^7 - 151548064*x^8 - 417242784*x^9 - 423562924*x^10 + 586224672*x^11 + 915719344*x^12 + 349980800*x^13 + 371621248*x^14 - 6541312*x^15 - 9691136*x^16 + 589824*x^17)/(1 - 22*x - 2351*x^2 - 40670*x^3 - 345038*x^4 - 3522884*x^5 - 28528327*x^6 - 145350120*x^7 - 623982088*x^8 - 2110011040*x^9 - 1354478796*x^10 + 9281598624*x^11 + 15001687984*x^12 + 3456230016*x^13 - 3194643904*x^14 - 1637793792*x^15 - 575934464*x^16 + 65175552*x^17).
a(n) = 22*a(n-1) + 2351*a(n-2) + 40670*a(n-3) + 345038*a(n-4) + 3522884*a(n-5) + 28528327*a(n-6) + 145350120*a(n-7) + 623982088*a(n-8) + 2110011040*a(n-9) + 1354478796*a(n-10) - 9281598624*a(n-11) - 15001687984*a(n-12) - 3456230016*a(n-13) + 3194643904*a(n-14) + 1637793792*a(n-15) + 575934464*a(n-16) - 65175552*a(n-17) for n>16.
Showing 1-8 of 8 results.