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 10 results.

A227690 Number A(n,k) of tilings of a k X n rectangle using integer-sided square tiles reduced for symmetry; 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, 2, 2, 1, 1, 1, 1, 4, 3, 4, 1, 1, 1, 1, 5, 6, 6, 5, 1, 1, 1, 1, 9, 10, 13, 10, 9, 1, 1, 1, 1, 12, 21, 39, 39, 21, 12, 1, 1, 1, 1, 21, 39, 115, 77, 115, 39, 21, 1, 1, 1, 1, 30, 82, 295, 521, 521, 295, 82, 30, 1, 1
Offset: 0

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Author

Keywords

Examples

			Square array A(n,k) begins:
  1, 1,  1,  1,   1,    1,     1,      1,       1, ...
  1, 1,  1,  1,   1,    1,     1,      1,       1, ...
  1, 1,  2,  2,   4,    5,     9,     12,      21, ...
  1, 1,  2,  3,   6,   10,    21,     39,      82, ...
  1, 1,  4,  6,  13,   39,   115,    295,     861, ...
  1, 1,  5, 10,  39,   77,   521,   1985,    8038, ...
  1, 1,  9, 21, 115,  521,  1494,  15129,   83609, ...
  1, 1, 12, 39, 295, 1985, 15129,  56978,  861159, ...
  1, 1, 21, 82, 861, 8038, 83609, 861159, 4495023, ...
...
A(4,3) = 6 because there are 6 ways to tile a 3 X 4 rectangle by subsquares, reduced for symmetry, i.e., where rotations and reflections are not counted as distinct:
   ._____ _.    ._______.    ._______.
   |     |_|    |   |   |    |   |_|_|
   |     |_|    |___|_ _|    |___|   |
   |_____|_|    |_|_|_|_|    |_|_|___|
   ._______.    ._______.    ._______.
   |   |_|_|    |_|   |_|    |_|_|_|_|
   |___|_|_|    |_|___|_|    |_|_|_|_|
   |_|_|_|_|    |_|_|_|_|    |_|_|_|_|
		

Crossrefs

A359020 Number of inequivalent tilings of a 4 X n rectangle using integer-sided square tiles.

Original entry on oeis.org

1, 1, 4, 6, 13, 39, 115, 295, 861, 2403, 7048, 20377, 60008, 175978, 519589, 1532455, 4531277, 13395656, 39639758, 117301153, 347248981, 1028011708, 3043852214, 9012879842, 26689014028, 79033362580, 234045889421, 693101137571, 2052569508948
Offset: 0

Views

Author

John Mason, Dec 12 2022

Keywords

Examples

			a(3) is 6 because of:
  +-+-+-+ +-+-+-+ +-+-+-+ +-+-+-+ +-+-+-+ +-+-+-+
  | | | | |     | |   | | |   | | |   | | | | | |
  +-+-+-+ +     + +   +-+ +   +-+ +   +-+ +-+-+-+
  | | | | |     | |   | | |   | | |   | | |   | |
  +-+-+-+ +     + +-+-+-+ +-+-+-+ +-+-+-+ +   +-+
  | | | | |     | |   | | | |   | | | | | |   | |
  +-+-+-+ +-+-+-+ +   +-+ +-+   + +-+-+-+ +-+-+-+
  | | | | |     | |   | | | |   | | | | | | | | |
  +-+-+-+ +-+-+-+ +-+-+-+ +-+-+-+ +-+-+-+ +-+-+-+
		

Crossrefs

Column k = 4 of A227690.
Sequences for fixed and free (inequivalent) tilings of m X n rectangles, for 2 <= m <= 10:

Formula

For even n > 4
a(n) = (A054856(n) + compo(n) + 4 * A054856((n - 2) / 2) +
2 * A054856((n - 4) / 2) + 2 * A054856(n / 2) +
2 * Sum_{k=0..(n - 2) / 2} (A054856(k))) / 4
For odd n > 4
a(n) = (A054856(n) + compo(n) + 2 * A054856((n - 3) / 2) +
2 * A054856((n - 1) / 2) + 2 * Sum_ {k=0..(n - 3) / 2} (A054856(k))) / 4
Where compo(n) is the number of distinct compositions of n as a sum of 1, 2, (1+1) and 4.

A359021 Number of inequivalent tilings of a 5 X n rectangle using integer-sided square tiles.

Original entry on oeis.org

1, 1, 5, 10, 39, 77, 521, 1985, 8038, 32097, 130125, 525676, 2131557, 8635656, 35017970, 141968455, 575692056, 2334344849, 9465939422, 38384559168, 155652202456, 631178976378, 2559476952229, 10378857744374, 42087027204278, 170665938023137, 692062856184512
Offset: 0

Views

Author

John Mason, Dec 12 2022

Keywords

Examples

			a(2) is 5 because of:
  +-+-+ +-+-+ +-+-+ +-+-+ +-+-+
  | | | |   | |   | |   | |   |
  +-+-+ +-+-+ +   + +   + +-+-+
  | | | |   | |   | |   | |   |
  +-+-+ +   + +-+-+ +-+-+ +   +
  | | | |   | |   | | | | |   |
  +-+-+ +-+-+ +-+-+ +-+-+ +-+-+
  | | | |   | |   | | | | | | |
  +-+-+ +   + +   + +-+-+ +-+-+
  | | | |   | |   | | | | | | |
  +-+-+ +-+-+ +-+-+ +-+-+ +-+-+
		

Crossrefs

Column k = 5 of A227690.
Sequences for fixed and free (inequivalent) tilings of m X n rectangles, for 2 <= m <= 10:
Cf. A079975.

Formula

For even n > 5:
a(n) = (A054857(n) + A079975(n) + 2*A054857(n/2) + 2* fixed_md(n/2) + 2*A054857((n-4)/2) + 4*A054857((n-2)/2) + 2* (A054857((n/2)-1) + fixed_md((n/2)-1)))/4.
For odd n > 5:
a(n) = (A054857(n) + A079975(n) + 2*A054857((n-1)/2) + 4*A054857((n-3)/2) + 2*fixed_md((n-3)/2) + 2*A054857((n-5)/2) + 2*fixed_md((n-1)/2))/4.
where
fixed_md(1)=1, fixed_md(2)=3, fixed_md(3)=15 and for n > 3, fixed_md(n) = A054857(n-1) + A054857(n-2) + fixed_md(n-2)+ fixed_md(n-1) + 2*A054857(n-3) + fixed_md(n-3).

A359022 Number of inequivalent tilings of a 6 X n rectangle using integer-sided square tiles.

Original entry on oeis.org

1, 1, 9, 21, 115, 521, 1494, 15129, 83609, 459957, 2551794, 14150081, 78597739
Offset: 0

Views

Author

John Mason, Dec 12 2022

Keywords

Crossrefs

Column k = 6 of A227690.
Sequences for fixed and free (inequivalent) tilings of m X n rectangles, for 2 <= m <= 10:

A359023 Number of inequivalent tilings of a 7 X n rectangle using integer-sided square tiles.

Original entry on oeis.org

1, 1, 12, 39, 295, 1985, 15129, 56978, 861159, 6542578, 49828415
Offset: 0

Views

Author

John Mason, Dec 12 2022

Keywords

Crossrefs

Column k = 7 of A227690.
Sequences for fixed and free (inequivalent) tilings of m X n rectangles, for 2 <= m <= 10:

A359024 Number of inequivalent tilings of an 8 X n rectangle using integer-sided square tiles.

Original entry on oeis.org

1, 1, 21, 82, 861, 8038, 83609, 861159, 4495023
Offset: 0

Views

Author

John Mason, Dec 12 2022

Keywords

Crossrefs

Column k = 8 of A227690.
Sequences for fixed and free (inequivalent) tilings of m X n rectangles, for 2 <= m <= 10:

A359025 Number of inequivalent tilings of a 9 X n rectangle using integer-sided square tiles.

Original entry on oeis.org

1, 1, 30, 163, 2403, 32097, 459957, 6542578, 93604244
Offset: 0

Views

Author

John Mason, Dec 12 2022

Keywords

Crossrefs

Column k = 9 of A227690.
Sequences for fixed and free (inequivalent) tilings of m X n rectangles, for 2 <= m <= 10:

A359026 Number of inequivalent tilings of a 10 X n rectangle using integer-sided square tiles.

Original entry on oeis.org

1, 1, 51, 347, 7048, 130125, 2551794, 49828415
Offset: 0

Views

Author

John Mason, Dec 12 2022

Keywords

Crossrefs

Column k = 10 of A227690.
Sequences for fixed and free (inequivalent) tilings of m X n rectangles, for 2 <= m <= 10:

A362261 Maximum number of ways in which a set of integer-sided squares can tile an n X 3 rectangle, up to rotations and reflections.

Original entry on oeis.org

1, 1, 1, 1, 2, 4, 8, 12, 22, 40, 73, 146, 292, 560, 1120, 2532, 5040, 10080, 22176, 44352, 88704, 192272, 384384, 768768, 1647360, 3294720, 6589440, 14003120, 28006240, 56012480, 126028080, 266053680, 532107360, 1182438400, 2483130720, 4966261440, 10925775168
Offset: 0

Views

Author

Pontus von Brömssen, Apr 15 2023

Keywords

Crossrefs

Third column of A362258.
Cf. A359019, A361225 (rectangular pieces), A362144.

Programs

  • Python
    from math import comb
    def F(i,j,k):
        # total number of tilings using i, j, and 2*j+3*k squares of side lengths 3, 2, and 1, respectively
        return comb(i+j+k,i)*comb(j+k,j)*2**j
    def F0(i,j,k):
        # number of inequivalent tilings
        x = F(i,j,k)
        if j == 0: x += comb(i+k,i) # horizontal line of symmetry
        if i%2+j%2+k%2 <= 1: x += 2*F(i//2,j//2,k//2) # vertical line of symmetry or rotational symmetry
        return x//4
    def A362261(n):
        return max(F0(i,j,n-3*i-2*j) for i in range(n//3+1) for j in range((n-3*i)//2+1))

Formula

a(n) >= A362144(n)/4.

A361525 Number of ways of dividing an n X 3 rectangle into integer-sided rectangles, up to rotations and reflections.

Original entry on oeis.org

1, 3, 17, 54, 892, 8159, 80021, 791821, 7906439, 79069308
Offset: 0

Views

Author

Pontus von Brömssen, Mar 15 2023

Keywords

Crossrefs

Third column of A361523.
Cf. A208215 (rotations and reflections are considered distinct), A359019 (square pieces), A360632.

Formula

a(n) >= A208215(n)/4 for n != 3.
a(n) ~ A208215(n)/4.
Showing 1-10 of 10 results.