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 1-10 of 15 results. Next

A063443 Number of ways to tile an n X n square with 1 X 1 and 2 X 2 tiles.

Original entry on oeis.org

1, 1, 2, 5, 35, 314, 6427, 202841, 12727570, 1355115601, 269718819131, 94707789944544, 60711713670028729, 69645620389200894313, 144633664064386054815370, 540156683236043677756331721, 3641548665525780178990584908643, 44222017282082621251230960522832336
Offset: 0

Views

Author

Reiner Martin, Jul 23 2001

Keywords

Comments

a(n) is also the number of ways to populate an n-1 X n-1 chessboard with nonattacking kings (including the case of zero kings). Cf. A193580. - Andrew Woods, Aug 27 2011
Also the number of vertex covers and independent vertex sets of the n-1 X n-1 king graph.

References

  • Steven R. Finch, Mathematical Constants, Cambridge, 2003, p. 343

Crossrefs

a(n) = row sum n-1 of A193580.
Main diagonal of A245013.

Programs

  • Mathematica
    Needs["LinearAlgebra`MatrixManipulation`"] Remove[mat] step[sa[rules1_, {dim1_, dim1_}], sa[rules2_, {dim2_, dim2_}]] := sa[Join[rules2, rules1 /. {x_Integer, y_Integer} -> {x + dim2, y}, rules1 /. {x_Integer, y_Integer} -> {x, y + dim2}], {dim1 + dim2, dim1 + dim2}] mat[0] = sa[{{1, 1} -> 1}, {1, 1}]; mat[1] = sa[{{1, 1} -> 1, {1, 2} -> 1, {2, 1} -> 1}, {2, 2}]; mat[n_] := mat[n] = step[mat[n - 2], mat[n - 1]]; A[n_] := mat[n] /. sa -> SparseArray; F[n_] := MatrixPower[A[n], n + 1][[1, 1]]; (* Mark McClure (mcmcclur(AT)bulldog.unca.edu), Mar 19 2006 *)
    $RecursionLimit = 1000; Clear[a, b]; b[n_, l_List] := b[n, l] = Module[{m=Min[l], k}, If[m>0, b[n-m, l-m], If[n == 0, 1, k=Position[l, 0, 1, 1][[1, 1]]; b[n, ReplacePart[l, k -> 1]] + If[n>1 && k 2, k+1 -> 2}]], 0]]]]; a[n_] := a[n] = If[n<2, 1, b[n, Table[0, {n}]]]; Table[Print[a[n]]; a[n], {n, 0, 17}] (* Jean-François Alcover, Dec 11 2014, after Alois P. Heinz *)

Formula

Lim_{n -> infinity} (a(n))^(1/n^2) = A247413 = 1.342643951124... . - Brendan McKay, 1996

Extensions

4 more terms from R. H. Hardin, Jan 23 2002
2 more terms from Keith Schneider (kschneid(AT)bulldog.unca.edu), Mar 19 2006
5 more terms from Andrew Woods, Aug 27 2011
a(22)-a(24) in b-file from Vaclav Kotesovec, May 01 2012
a(0) inserted by Alois P. Heinz, Sep 17 2014
a(25)-a(40) in b-file from Johan Nilsson, Mar 10 2016

A245013 Number A(n,k) of tilings of a k X n rectangle using 1 X 1 squares and 2 X 2 squares; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 3, 3, 1, 1, 1, 1, 5, 5, 5, 1, 1, 1, 1, 8, 11, 11, 8, 1, 1, 1, 1, 13, 21, 35, 21, 13, 1, 1, 1, 1, 21, 43, 93, 93, 43, 21, 1, 1, 1, 1, 34, 85, 269, 314, 269, 85, 34, 1, 1, 1, 1, 55, 171, 747, 1213, 1213, 747, 171, 55, 1, 1
Offset: 0

Views

Author

Alois P. Heinz, Sep 16 2014

Keywords

Examples

			A(3,3) = 5:
  ._._._.  .___._.  ._.___.  ._._._.  ._._._.
  |_|_|_|  |   |_|  |_|   |  |_|_|_|  |_|_|_|
  |_|_|_|  |___|_|  |_|___|  |_|   |  |   |_|
  |_|_|_|  |_|_|_|  |_|_|_|  |_|___|  |___|_| .
Square array A(n,k) begins:
  1, 1,  1,  1,   1,    1,     1,      1, ...
  1, 1,  1,  1,   1,    1,     1,      1, ...
  1, 1,  2,  3,   5,    8,    13,     21, ...
  1, 1,  3,  5,  11,   21,    43,     85, ...
  1, 1,  5, 11,  35,   93,   269,    747, ...
  1, 1,  8, 21,  93,  314,  1213,   4375, ...
  1, 1, 13, 43, 269, 1213,  6427,  31387, ...
  1, 1, 21, 85, 747, 4375, 31387, 202841, ...
		

Crossrefs

Columns (or rows) k=0+1,2-10 give: A000012, A000045(n+1), A001045(n+1), A054854, A054855, A063650, A063651, A063652, A063653, A063654.
Main diagonal gives A063443.

Programs

  • Maple
    b:= proc(n, l) option remember; local m, k; m:= min(l[]);
          if m>0 then b(n-m, map(x->x-m, l))
        elif n=0 then 1
        else for k while l[k]>0 do od; b(n, subsop(k=1, l))+
             `if`(n>1 and k `if`(min(n, k)<2, 1, b(max(n, k), [0$min(n, k)])):
    seq(seq(A(n, d-n), n=0..d), d=0..14);
  • Mathematica
    b[n_, l_] := b[n, l] = Module[{m=Min[l], k}, If[m>0, b[n-m, l-m], If[n == 0, 1, k=Position[l, 0, 1, 1][[1, 1]]; b[n, ReplacePart[l, k -> 1]] + If[n>1 && k 2, k+1 -> 2}]], 0]]]]; A[n_, k_] := If[Min[n, k]<2, 1, b[Max[n, k], Table[0, {Min[n, k]}]]]; Table[Table[A[n, d-n], {n, 0, d}], {d, 0, 14}] // Flatten (* Jean-François Alcover, Dec 11 2014, after Alois P. Heinz *)

A226322 Number of tilings of a 4 X n rectangle using L tetrominoes and 2 X 2 tiles.

Original entry on oeis.org

1, 0, 3, 6, 19, 48, 141, 378, 1063, 2920, 8115, 22418, 62123, 171876, 475919, 1317250, 3646681, 10094356, 27943739, 77353070, 214129845, 592752572, 1640859689, 4542223926, 12573787053, 34806745800, 96352029241, 266721635838, 738338745535, 2043868995512
Offset: 0

Views

Author

Alois P. Heinz, Jun 03 2013

Keywords

Examples

			a(3) = 6:
._____.  ._____.  .___._.  ._.___.  ._____.  ._____.
| .___|  |___. |  |   | |  | |   |  |___. |  | .___|
|_|_. |  | ._|_|  |___| |  | |___|  |   |_|  |_|   |
|   | |  | |   |  | |___|  |___| |  |___| |  | |___|
|___|_|  |_|___|  |_____|  |_____|  |_____|  |_____|
		

Crossrefs

Programs

  • Maple
    a:= n-> (Matrix(12, (i, j)-> `if`(i+1=j, 1, `if`(i=12,
        [-2, 0, -4, -2, -3, 0, -1, 0, 4, 6, 5, 0][j], 0)))^(n+8).
        <<-1, 0, 1/2, [0$5][], 1, 0, 3, 6>>)[1, 1]:
    seq(a(n), n=0..40);
  • Mathematica
    a[n_] := MatrixPower[ Table[ If[i+1 == j, 1, If[i == 12, {-2, 0, -4, -2, -3, 0, -1, 0, 4, 6, 5, 0}[[j]], 0]], {i, 1, 12}, {j, 1, 12}], n+8].{-1, 0, 1/2, 0, 0, 0, 0, 0, 1, 0, 3, 6} // First; Table[a[n], {n, 0, 40}] (* Jean-François Alcover, Dec 05 2013, after Maple *)

Formula

G.f.: (x^6+2*x^2-1) / (-2*x^12 -4*x^10 -2*x^9 -3*x^8 -x^6 +4*x^4 +6*x^3 +5*x^2-1).

A054855 Number of ways to tile a 5 X n area with 1 X 1 and 2 X 2 tiles.

Original entry on oeis.org

1, 1, 8, 21, 93, 314, 1213, 4375, 16334, 59925, 221799, 817280, 3018301, 11134189, 41096528, 151643937, 559640289, 2065192514, 7621289593, 28124714395, 103789150046, 383013144129, 1413437041011, 5216013647648, 19248692843977
Offset: 0

Views

Author

Silvia Heubach (silvi(AT)cine.net), Apr 21 2000

Keywords

Examples

			a(2)=8 as there is one tiling of a 5 X 2 area with only 1 X 1 tiles, 4 tilings with exactly one 2 X 2 tile and 3 tilings with exactly two 2 X 2 tiles.
		

Crossrefs

Column k=5 of A245013.

Programs

  • Mathematica
    f[{A_, B_}] := Module[{til = A, basic = B}, {Flatten[Append[til, ListConvolve[A, B]]], AppendTo[basic, 2 Fibonacci[Length[B] + 2]]}]; NumOfTilings[n_] := Nest[f, {{1, 1}, {1, 7}}, n - 2][[1]] NumOfTilings[30]

Formula

a(n) = b(1)a(n-1)+b(2)a(n-2)+...+b(n)a(0), where a(0)=a(1)=1 and b(1)=1, b(2)=7, b(n)=F(n+1)of A000045 (Fibonacci numbers) for n>2.
a(n) = 2*a(n-1) + 7*a(n-2) - 2*a(n-3) - 3*a(n-4). - Keith Schneider (kschneid(AT)bulldog.unca.edu), Apr 02 2006
G.f.: (1-x-x^2)/(1-2*x-7*x^2+2*x^3+3*x^4). [R. J. Mathar, Nov 02 2008]

A063650 Number of ways to tile a 6 X n rectangle with 1 X 1 and 2 X 2 tiles.

Original entry on oeis.org

1, 1, 13, 43, 269, 1213, 6427, 31387, 159651, 795611, 4005785, 20064827, 100764343, 505375405, 2536323145, 12724855013, 63851706457, 320373303983, 1607526474153, 8065864257905, 40471399479495, 203068825478591, 1018918472214687, 5112520236292975, 25652573037707685
Offset: 0

Views

Author

Reiner Martin, Jul 23 2001

Keywords

Crossrefs

Column k=6 of A245013.

Programs

  • Magma
    I:=[1,1,13,43,269,1213]; [n le 6 select I[n] else 2*Self(n-1)+16*Self(n-2)+Self(n-3)-27*Self(n-4)+Self(n-5)+4*Self(n-6): n in [1..30]]; // Vincenzo Librandi, Oct 30 2018
  • Mathematica
    LinearRecurrence[{2, 16, 1, -27, 1, 4}, {1, 1, 13, 43, 269, 1213}, 22] (* Jean-François Alcover, Oct 30 2018 *)
    CoefficientList[Series[(-1+x+5*x^2-x^4)/(-1+2*x+16*x^2+x^3-27*x^4+x^5+4*x^6), {x, 0, 50}], x] (* Stefano Spezia, Oct 30 2018 *)

Formula

G.f.: ( -1+x+5*x^2-x^4 ) / ( -1+2*x+16*x^2+x^3-27*x^4+x^5+4*x^6 ).
a(n) = 2a(n-1) + 16a(n-2) + a(n-3) - 27a(n-4) + a(n-5) + 4a(n-6) - Keith Schneider (kschneid(AT)bulldog.unca.edu), Apr 02 2006

A165791 Number of tilings of a 4 X n rectangle using dominoes and right trominoes.

Original entry on oeis.org

1, 1, 11, 55, 380, 2319, 15171, 96139, 619773, 3962734, 25445515, 163048957, 1045897075, 6705473761, 43001795070, 275730928993, 1768128097215, 11337760387473, 72702310606249, 466192677008538, 2989403530821497, 19169143325987983, 122919655766448729
Offset: 0

Views

Author

Alois P. Heinz, Sep 26 2009

Keywords

Examples

			a(2) = 11, because there are 11 tilings of a 4 X 2 rectangle using dominoes and right trominoes:
  .___. .___. .___. ._._. ._._. .___. .___. .___. .___. .___. .___.
  |___| |___| |_._| | | | | | | |___| |___| | ._| |_. | | ._| |_. |
  |___| |_._| | | | |_|_| |_|_| | ._| |_. | |_| | | |_| |_| | | |_|
  |___| | | | |_|_| |___| | | | |_| | | |_| |___| |___| | |_| |_| |
  |___| |_|_| |___| |___| |_|_| |___| |___| |___| |___| |___| |___|  .
		

Crossrefs

Column k=4 of A219987.

Programs

  • Maple
    a:= n-> (Matrix([[619773, 96139, 15171, 2319, 380, 55, 11, 1, 1]]). Matrix(9, (i,j)-> if i=j-1 then 1 elif j=1 then [4, 21, -25, -65, -17, 24, -11, -15, 9][i] else 0 fi)^n)[1,9]: seq(a(n), n=0..25);
  • Mathematica
    a[n_] := {619773, 96139, 15171, 2319, 380, 55, 11, 1, 1} . MatrixPower[ Table[ Which[i == j-1, 1, j == 1, {4, 21, -25, -65, -17, 24, -11, -15, 9}[[i]], True, 0], {i, 1, 9}, {j, 1, 9}], n] // Last; Table[a[n], {n, 0, 25}] (* Jean-François Alcover, Dec 04 2013, translated and adapted from Alois P. Heinz's Maple program *)

Formula

G.f.: (2*x^8-5*x^7+2*x^6-x^5-19*x^4-15*x^3+14*x^2+3*x-1) / (9*x^9-15*x^8-11*x^7+24*x^6-17*x^5-65*x^4-25*x^3+21*x^2+4*x-1).

A063654 Number of ways to tile a 10 X n rectangle with 1 X 1 and 2 X 2 tiles.

Original entry on oeis.org

1, 1, 89, 683, 16717, 221799, 4005785, 61643709, 1029574631, 16484061769, 269718819131, 4364059061933, 71019435701025, 1152314664726905, 18725412666911121, 304052089851133193, 4939032362569285343
Offset: 0

Views

Author

Reiner Martin, Jul 23 2001

Keywords

Crossrefs

Column k=10 of A245013.

Formula

a(n) = 11a(n-1) + 195a(n-2) - 1459a(n-3) - 10427a(n-4) + 79002a(n-5) + 188873a(n-6) - 1922453a(n-7) - 522744a(n-8) + 21726132a(n-9) - 11085988a(n-10) - 137059276a(n-11) + 114023550a(n-12) + 533938164a(n-13) - 503739499a(n-14) - 1345858084a(n-15) + 1272444796a(n-16) + 2223076291a(n-17) - 1997887777a(n-18) - 2382027317a(n-19) + 2015253425a(n-20) + 1613022647a(n-21) - 1309632545a(n-22) - 660948344a(n-23) + 533727589a(n-24) + 152685069a(n-25) - 128889883a(n-26) - 17772195a(n-27) + 16954690a(n-28) + 883980a(n-29) - 1089264a(n-30) - 11392a(n-31) + 26112a(n-32) - Keith Schneider (kschneid(AT)bulldog.unca.edu), Apr 02 2006

A165799 Number of tilings of a 4 X n rectangle using right trominoes and 2 X 2 tiles.

Original entry on oeis.org

1, 0, 1, 4, 6, 16, 37, 92, 245, 560, 1426, 3720, 9069, 22808, 58177, 145660, 366318, 925536, 2331269, 5872212, 14802941, 37311528, 94038250, 236999064, 597348237, 1505640016, 3794761257, 9564393972, 24106951622, 60759989040, 153141435269, 385986293964
Offset: 0

Views

Author

Alois P. Heinz, Sep 27 2009

Keywords

Examples

			a(4) = 6, because there are 6 tilings of a 4 X 4 rectangle using right trominoes and 2 X 2 tiles:
  .___.___. .___.___. .___.___. .___.___. .___.___. .___.___.
  | . | . | | ._|_. | | ._| . | | ._|_. | | ._|_. | | . |_. |
  |___|___| |_| . |_| |_| |___| |_| ._|_| |_|_. |_| |___| |_|
  | . | . | | |___| | | |___| | | |_| . | | . |_| | | |___| |
  |___|___| |___|___| |___|___| |___|___| |___|___| |___|___|
		

Crossrefs

Column k=4 of A219946.

Programs

  • Maple
    a:= n-> (Matrix([[4, 1, 0, 1, 0$5]]). Matrix(9, (i,j)-> if i=j-1 then 1 elif j=1 then [1, 1, 9, 1, -3, -22, -16, 0, -4][i] else 0 fi)^n)[1,4]: seq(a(n), n=0..30);
  • Mathematica
    Series[ (-6*x^3 - x + 1) / (4*x^9 + 16*x^7 + 22*x^6 + 3*x^5 - x^4 - 9*x^3 - x^2 - x + 1), {x, 0, 31}] // CoefficientList[#, x] & (* Jean-François Alcover, Jun 18 2013, after Alois P. Heinz *)
    LinearRecurrence[{1,1,9,1,-3,-22,-16,0,-4},{1,0,1,4,6,16,37,92,245},40] (* Harvey P. Dale, Nov 09 2024 *)

Formula

G.f.: -(6*x^3+x-1) / (4*x^9+16*x^7+22*x^6+3*x^5-x^4-9*x^3-x^2-x+1).
a(n) = a(n-1) +a(n-2) +9*a(n-3) +a(n-4) -3*a(n-5) -22*a(n-6) -16*a(n-7) -4*a(n-9).

A063652 Number of ways to tile an 8 X n rectangle with 1 X 1 and 2 X 2 tiles.

Original entry on oeis.org

1, 1, 34, 171, 2115, 16334, 159651, 1382259, 12727570, 113555791, 1029574631, 9258357134, 83605623809, 753361554685, 6795928721858, 61270295494859, 552555688390363, 4982395765808506, 44929655655496287, 405145692220245539, 3653405881837027898
Offset: 0

Views

Author

Reiner Martin, Jul 23 2001

Keywords

Crossrefs

Column k=8 of A245013.

Formula

a(n) = 6a(n-1) + 50a(n-2) - 171a(n-3) - 514a(n-4) + 1800a(n-5) + 845a(n-6) - 5430a(n-7) + 704a(n-8) + 6175a(n-9) - 1762a(n-10) - 2810a(n-11) + 870a(n-12) + 392a(n-13) - 120a(n-14). - Keith Schneider (kschneid(AT)bulldog.unca.edu), Apr 02 2006
G.f.: ( 1 -5*x -22*x^2 +88*x^3 +74*x^4 -378*x^5 -31*x^6 +597*x^7 -114*x^8 -336*x^9 +94*x^10 +52*x^11 -16*x^12 ) / ( 1 -6*x -50*x^2 +171*x^3 +514*x^4 -1800*x^5 -845*x^6 +5430*x^7 -704*x^8 -6175*x^9 +1762*x^10 +2810*x^11 -870*x^12 -392*x^13 +120*x^14 ). - R. J. Mathar, Dec 19 2015

A063653 Number of ways to tile a 9 X n rectangle with 1 X 1 and 2 X 2 tiles.

Original entry on oeis.org

1, 1, 55, 341, 5933, 59925, 795611, 9167119, 113555791, 1355115601, 16484061769, 198549329897, 2403674442213, 29023432116879, 350917980468767, 4239961392742933, 51247532773412135, 619304595300705203, 7484739788762129061, 90454037365096154821
Offset: 0

Views

Author

Reiner Martin, Jul 23 2001

Keywords

Comments

a(8) is number of ways can kings be placed on an 8 X 8 chessboard so that no two kings can attack each other. - Vaclav Kotesovec, Apr 02 2010

Crossrefs

Formula

a(n) = 6*a(n-1) + 110*a(n-2) - 262*a(n-3) - 2786*a(n-4) + 5916*a(n-5) + 25168*a(n-6) - 53907*a(n-7) - 95299*a(n-8) + 197820*a(n-9) + 193866*a(n-10) - 340168*a(n-11) - 228528*a(n-12) + 279636*a(n-13) + 137864*a(n-14) - 108909*a(n-15) - 33736*a(n-16) + 20214*a(n-17) + 2460*a(n-18) - 1296*a(n-19).

Extensions

Subscripts in formula repaired by Ron Hardin, Dec 29 2010
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