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 26 results. Next

A001168 Number of fixed polyominoes with n cells.

Original entry on oeis.org

1, 1, 2, 6, 19, 63, 216, 760, 2725, 9910, 36446, 135268, 505861, 1903890, 7204874, 27394666, 104592937, 400795844, 1540820542, 5940738676, 22964779660, 88983512783, 345532572678, 1344372335524, 5239988770268, 20457802016011, 79992676367108, 313224032098244, 1228088671826973
Offset: 0

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Author

Keywords

Comments

Number of rookwise connected patterns of n square cells.
N. Madras proved in 1999 the existence of lim_{n->oo} a(n+1)/a(n), which is the real limit growth rate of the number of polyominoes; and hence, this limit is equal to lim_{n->oo} a(n)^{1/n}, the well-known Klarner's constant. The currently best-known lower and upper bounds on this constant are 3.9801 (Barequet et al., 2006) and 4.6496 (Klarner and Rivest, 1973), respectively. But see also Knuth (2014).

Examples

			a(0) = 1 as there is 1 empty polyomino with #cells = 0. - _Fred Lunnon_, Jun 24 2020
		

References

  • Steven R. Finch, Mathematical Constants, Cambridge, 2003, pp. 378-382.
  • J. E. Goodman and J. O'Rourke, editors, Handbook of Discrete and Computational Geometry, CRC Press, 1997, p. 229.
  • A. J. Guttmann, ed., Polygons, Polyominoes and Polycubes, Springer, 2009, p. 478. (Table 16.10 has 56 terms of this sequence.)
  • I. Jensen. Counting polyominoes: a parallel implementation for cluster computing. LNCS 2659 (2003) 203-212, ICCS 2003
  • W. F. Lunnon, Counting polyominoes, pp. 347-372 of A. O. L. Atkin and B. J. Birch, editors, Computers in Number Theory. Academic Press, NY, 1971.
  • W. F. Lunnon, Counting hexagonal and triangular polyominoes, pp. 87-100 of R. C. Read, editor, Graph Theory and Computing. Academic Press, NY, 1972.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Cf. A000105, A000988, A006746, A056877, A006748, A056878, A006747, A006749, A142886, A144553, row sums of A308359, A210986 (bisection), A210987 (bisection).
A006762 is another version.
Excluding a(0), 8th and 9th row of A366767.

Programs

  • Mathematica
    See Jaime Rangel-Mondragón's article.

Formula

For asymptotics, see Knuth (2014).
a(n) = 8*A006749(n) + 4*A006746(n) + 4*A006748(n) + 4*A006747(n) + 2*A056877(n) + 2*A056878(n) + 2*A144553(n) + A142886(n); the number of fixed polyominoes is calculatable according to multiples of the numbers of the various symmetries of the polyomino. - John Mason, Sep 06 2017

Extensions

Extended to n=28 by Tomás Oliveira e Silva
Extended to n=46 by Iwan Jensen
Verified (and one more term found) by Don Knuth, Jan 09 2001
Richard C. Schroeppel communicated Jensen's calculation of the first 56 terms, Feb 21 2005
Gill Barequet commented on Madras's proof from 1999 of the limit growth rate of this sequence, and provided references to the currently best-known bounds on it, May 24 2011
Incorrect Mathematica program removed by Jean-François Alcover, Mar 24 2015
a(0) = 1 added by N. J. A. Sloane, Jun 24 2020

A366766 Array read by antidiagonals, where each row is the counting sequence of a certain type of free polyominoids (see comments).

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 3, 2, 1, 0, 1, 0, 1, 7, 5, 0, 1, 0, 1, 0, 1, 20, 16, 0, 1, 1, 0, 1, 0, 1, 60, 55, 0, 2, 1, 1, 0, 1, 0, 1, 204, 222, 0, 5, 2, 2, 1, 0, 1, 0, 1, 702, 950, 0, 12, 5, 5, 0, 1
Offset: 1

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Author

Pontus von Brömssen, Oct 22 2023

Keywords

Comments

A (D,d)-polyominoid is a connected set of d-dimensional unit cubes (cells) with integer coordinates in D-dimensional space. For normal polyominoids, two cells are connected if they share a (d-1)-dimensional facet, but here we allow connections where the cells share a lower-dimensional face.
Each row is the counting sequence (by number of cells) of (D,d)-polyominoids with certain restrictions on the allowed connections between cells. Two cells have a connection of type (g,h) if they intersect in a (d-g)-dimensional unit cube and extend in d-h common dimensions. For example, d-dimensional polyominoes use connections of type (1,0), polyplets use connections of types (1,0) (edge connections) and (2,0) (corner connections), normal (3,2)-polyominoids use connections of types (1,0) ("soft" connections) and (1,1) ("hard" connections), hard polyominoids use connections of type (1,1).
Each row corresponds to a triple (D,d,C), where 1 <= d <= D and C is a set of pairs (g,h) with 1 <= g <= d and 0 <= h <= min(g, D-d). The k-th term of that row is the number of free k-celled (D,d)-polyominoids with connections of the types in C. Connections of types not in C are permitted, but the polyominoids must be connected through the specified connections only. For example, polyominoes may have cells that intersect in a point (g = 2) and hard polyominoids can have soft connections (h = 0) that are not needed to keep the polyominoids connected.
The rows are sorted first by D, then by d, and finally by a binary vector indicating which types of connections are allowed, where the connection types (g,h) are sorted lexicographically. (See table in cross-references.)
For each pair (D,d), the first row is 1, 0, 0, ..., corresponding to (D,d,{}) (no connections allowed).
The number of rows corresponding to given values of D and d is 2^((d+1)*(d+2)/2-1) if 2*d <= D and 2^((D-d+1)*(3*d-D+2)/2-1) otherwise.

Examples

			Array begins:
  n\k| 1  2  3  4  5   6    7     8      9     10      11       12
  ---+------------------------------------------------------------
   1 | 1  0  0  0  0   0    0     0      0      0       0        0
   2 | 1  1  1  1  1   1    1     1      1      1       1        1
   3 | 1  0  0  0  0   0    0     0      0      0       0        0
   4 | 1  1  1  1  1   1    1     1      1      1       1        1
   5 | 1  1  3  7 20  60  204   702   2526   9180   33989   126713
   6 | 1  2  5 16 55 222  950  4265  19591  91678  434005  2073783
   7 | 1  0  0  0  0   0    0     0      0      0       0        0
   8 | 1  1  2  5 12  35  108   369   1285   4655   17073    63600
   9 | 1  1  2  5 12  35  108   369   1285   4655   17073    63600
  10 | 1  2  5 22 94 524 3031 18770 118133 758381 4915652 32149296
  11 | 1  0  0  0  0   0    0     0      0      0       0        0
  12 | 1  1  1  1  1   1    1     1      1      1       1        1
		

Crossrefs

Cf. A366767 (fixed), A366768.
The following table lists some sequences that are rows of the array, together with the corresponding values of D, d, and C. Some sequences occur in more than one row. Notation used in the table:
X: Allowed connection.
-: Not allowed connection (but may occur "by accident" as long as it is not needed for connectedness).
.: Not applicable for (D,d) in this row.
!: d < D and all connections have h = 0, so these polyominoids live in d < D dimensions only.
*: Whether a connection of type (g,h) is allowed or not is independent of h.
| | | connections |
| | | g:1122233334 |
n | D | d | h:0101201230 | sequence
----+---+---+--------------+---------
1 | 1 | 1 | * -......... | A063524
2 | 1 | 1 | * X......... | A000012
3 |!2 | 1 | * --........ | A063524
4 |!2 | 1 | X-........ | A000012
5 | 2 | 1 | -X........ | A361625
6 | 2 | 1 | * XX........ | A019988
7 | 2 | 2 | * -.-....... | A063524
8 | 2 | 2 | * X.-....... | A000105
9 | 2 | 2 | * -.X....... | A000105
10 | 2 | 2 | * X.X....... | A030222
11 |!3 | 1 | * --........ | A063524
12 |!3 | 1 | X-........ | A000012
13 | 3 | 1 | -X........ | A365654
14 | 3 | 1 | * XX........ | A365559
15 |!3 | 2 | * ----...... | A063524
16 |!3 | 2 | X---...... | A000105
17 | 3 | 2 | -X--...... | A365654
18 | 3 | 2 | * XX--...... | A075679
19 |!3 | 2 | --X-...... | A000105
20 |!3 | 2 | X-X-...... | A030222
21 | 3 | 2 | -XX-...... | A365995
22 | 3 | 2 | XXX-...... | A365997
23 | 3 | 2 | ---X...... | A365999
24 | 3 | 2 | X--X...... | A366001
25 | 3 | 2 | -X-X...... | A366003
26 | 3 | 2 | XX-X...... | A366005
27 | 3 | 2 | * --XX...... | A365652
28 | 3 | 2 | X-XX...... | A366007
29 | 3 | 2 | -XXX...... | A366009
30 | 3 | 2 | * XXXX...... | A365650
31 | 3 | 3 | * -.-..-.... | A063524
32 | 3 | 3 | * X.-..-.... | A038119
33 | 3 | 3 | * -.X..-.... | A038173
34 | 3 | 3 | * X.X..-.... | A268666
35 | 3 | 3 | * -.-..X.... | A038171
36 | 3 | 3 | * X.-..X.... | A363205
37 | 3 | 3 | * -.X..X.... | A363206
38 | 3 | 3 | * X.X..X.... | A272368
39 |!4 | 1 | * --........ | A063524
40 |!4 | 1 | X-........ | A000012
41 | 4 | 1 | -X........ | A366340
42 | 4 | 1 | * XX........ | A365561
43 |!4 | 2 | * -----..... | A063524
44 |!4 | 2 | X----..... | A000105
45 | 4 | 2 | -X---..... | A366338
46 | 4 | 2 | * XX---..... | A366334
47 |!4 | 2 | --X--..... | A000105
48 |!4 | 2 | X-X--..... | A030222
...
75 |!4 | 3 | * ----.--... | A063524
76 |!4 | 3 | X---.--... | A038119
77 | 4 | 3 | -X--.--... | A366340
78 | 4 | 3 | * XX--.--... | A366336
...
139 | 4 | 4 | * -.-..-...- | A063524
140 | 4 | 4 | * X.-..-...- | A068870
141 | 4 | 4 | * -.X..-...- | A365356
142 | 4 | 4 | * X.X..-...- | A365363
143 | 4 | 4 | * -.-..X...- | A365354
144 | 4 | 4 | * X.-..X...- | A365361
145 | 4 | 4 | * -.X..X...- | A365358
146 | 4 | 4 | * X.X..X...- | A365365
147 | 4 | 4 | * -.-..-...X | A365353
148 | 4 | 4 | * X.-..-...X | A365360
149 | 4 | 4 | * -.X..-...X | A365357
150 | 4 | 4 | * X.X..-...X | A365364
151 | 4 | 4 | * -.-..X...X | A365355
152 | 4 | 4 | * X.-..X...X | A365362
153 | 4 | 4 | * -.X..X...X | A365359
154 | 4 | 4 | * X.X..X...X | A365366
155 |!5 | 1 | * --........ | A063524
156 |!5 | 1 | X-........ | A000012
157 | 5 | 1 | -X........ |
158 | 5 | 1 | * XX........ | A365563

A001931 Number of fixed 3-dimensional polycubes with n cells; lattice animals in the simple cubic lattice (6 nearest neighbors), face-connected cubes.

Original entry on oeis.org

1, 3, 15, 86, 534, 3481, 23502, 162913, 1152870, 8294738, 60494549, 446205905, 3322769321, 24946773111, 188625900446, 1435074454755, 10977812452428, 84384157287999, 651459315795897, 5049008190434659, 39269513463794006, 306405169166373418
Offset: 1

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Keywords

Comments

This gives the number of polycubes up to translation (but not rotation or reflection). - Charles R Greathouse IV, Oct 08 2013

References

  • W. F. Lunnon, Symmetry of cubical and general polyominoes, pp. 101-108 of R. C. Read, editor, Graph Theory and Computing. Academic Press, NY, 1972.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Extensions

Edited by Arun Giridhar, Feb 14 2011
a(17) from Achim Flammenkamp, Feb 15 1999
a(18) from the Aleksandrowicz and Barequet paper (N. J. A. Sloane, Jul 09 2009)
a(19) from Luther and Mertens by Gill Barequet, Jun 12 2011
a(20) from Stanley Dodds, Aug 03 2023
a(21)-a(22) (using Dodds's algorithm) from Phillip Thompson, Feb 07 2024

A006770 Number of fixed n-celled polyominoes which need only touch at corners.

Original entry on oeis.org

1, 4, 20, 110, 638, 3832, 23592, 147941, 940982, 6053180, 39299408, 257105146, 1692931066, 11208974860, 74570549714, 498174818986, 3340366308393
Offset: 1

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Author

Keywords

Comments

Also known as fixed polyplets. - David Bevan, Jul 28 2009

Examples

			a(2)=4: the two fixed dominoes and the two rotations of the polyplet consisting of two cells touching at a vertex. - _David Bevan_, Jul 28 2009
a(3)=20 counts 4 rotations (by 0°, 45°, 90°, 135°) of the straight ... trinomino, and 8 rotations (by multiples of 45°) of the L-shaped .: trinomino and the ..· 3-polyplet, cf. link to the image. - _M. F. Hasler_, Sep 30 2014
		

References

  • D. H. Redelmeier, personal communication.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Cf. A030222 (free polyplets).
10th row of A366767.

Extensions

One more term from Joseph Myers, Sep 26 2002

A096267 Number of fixed polyedges with n edges (number of ways of embedding connected undirected graphs with n edges into the plane square lattice, inequivalent up to translation).

Original entry on oeis.org

2, 6, 22, 88, 372, 1628, 7312, 33466, 155446, 730534, 3466170, 16576874, 79810756, 386458826, 1880580352, 9190830700, 45088727820, 221945045488, 1095798917674, 5424898610958, 26922433371778, 133906343014110, 667370905196930, 3332257266746004
Offset: 1

Views

Author

Alexander Malkis, Jun 22 2004

Keywords

Comments

Found using the rooted method (also known as Redelmeier's algorithm).

Examples

			_|_|_ is a polyedge with 5 edges
		

Crossrefs

Cf. A019988 for "free" polyedges, A348096.
6th row of A366767.

Extensions

a(22)-a(24) from Mertens & Moore added by Andrey Zabolotskiy, Feb 01 2022

A075678 Number of fixed (orientation matters) polyominoids (shapes made of faces of cubes) with n squares.

Original entry on oeis.org

3, 18, 158, 1611, 17811, 207395, 2505858, 31125711, 394982973, 5098498323, 66733261455, 883602795509, 11814191512434, 159283419280014, 2163058572006613
Offset: 1

Views

Author

Joseph Myers, Sep 24 2002

Keywords

Crossrefs

Cf. A075679 (free), A056846.
18th row of A366767.

Extensions

a(13)-a(15) from John Mason, Mia Muessig, and Érika Roldán, Jul 04 2025

A383735 Array read by antidiagonals, where each row is the cluster series for percolation on the cells of a certain type of polyominoids.

Original entry on oeis.org

1, 0, 1, 0, 2, 1, 0, 2, 0, 1, 0, 2, 0, 2, 1, 0, 2, 0, 2, 4, 1, 0, 2, 0, 2, 12, 6, 1, 0, 2, 0, 2, 24, 18, 0, 1, 0, 2, 0, 2, 52, 48, 0, 4, 1, 0, 2, 0, 2, 108, 126, 0, 12, 4, 1, 0, 2, 0, 2, 224, 300, 0, 24, 12, 8, 1, 0, 2, 0, 2, 412, 762, 0, 52, 24, 32, 0, 1
Offset: 1

Views

Author

Pontus von Brömssen, May 10 2025

Keywords

Comments

T(n,k) is the coefficient of p^(k+1), k >= 0, in the power series expansion of the expected finite size of the cluster containing a given cell for percolation with probability p on the polyominoid cells corresponding to row n of A366766. If the given cell is not open, its cluster is empty. Equivalently, T(n,k) can be taken to be the coefficient of p^k if we condition on the event that the given cell is open.
See A366766 for details on how the polyominoids are specified and on the ordering of the rows.

Examples

			Array begins:
  n\k| 0  1  2   3   4    5    6    7     8     9     10     11      12
  ---+-----------------------------------------------------------------
   1 | 1  0  0   0   0    0    0    0     0     0      0      0       0
   2 | 1  2  2   2   2    2    2    2     2     2      2      2       2
   3 | 1  0  0   0   0    0    0    0     0     0      0      0       0
   4 | 1  2  2   2   2    2    2    2     2     2      2      2       2
   5 | 1  4 12  24  52  108  224  412   844  1528   3152   5036   11984
   6 | 1  6 18  48 126  300  762 1668  4216  8668  21988  43058  110832
   7 | 1  0  0   0   0    0    0    0     0     0      0      0       0
   8 | 1  4 12  24  52  108  224  412   844  1528   3152   5036   11984
   9 | 1  4 12  24  52  108  224  412   844  1528   3152   5036   11984
  10 | 1  8 32 108 348 1068 3180 9216 26452 73708 206872 563200 1555460
  11 | 1  0  0   0   0    0    0    0     0     0      0      0       0
  12 | 1  2  2   2   2    2    2    2     2     2      2      2       2
		

Crossrefs

Rows include:
n | sequence for row n
---+-------------------
1 | A000007
2 | A040000
3 | A000007
4 | A040000
5 | A003203
6 | A003198
7 | A000007
8 | A003203
9 | A003203
10 | A003201
11 | A000007
12 | A040000
13 | A383737
14 | A003207
15 | A000007
16 | A003203
17 | A383737
18 | A383736
19 | A003203
20 | A003201
...
31 | A000007
32 | A003211
33 | A003209
34 | A036396
35 | A003210
...
38 | A036402
39 | A000007
40 | A040000
...
43 | A000007
44 | A003203
...
47 | A003203
48 | A003201

Formula

T(n,k) = [p^k] Sum_P m^2*p^(m-1)*(1-p)^j / binomial(D,d) = Sum_P m^2*(-1)^(k-m+1)*binomial(j,k-m+1) / binomial(D,d), where the sum is over all fixed polyominoids P (corresponding to row n of A366766), m is the number of cells of P, and j is the number of cells that are not in P but are adjacent to a cell in P; d is the dimension of the cells and D is the dimension of the ambient space. It is sufficient to take the sums over those P that have at most k+1 cells.

A365560 Number of fixed n-polysticks (or polyedges) in 3 dimensions.

Original entry on oeis.org

3, 15, 95, 681, 5277, 43086, 365313, 3186444, 28414802, 257908020, 2375037477, 22136623447, 208438845633, 1979867655945, 18948498050586, 182549617674339, 1768943859449895, 17230208981859485
Offset: 1

Views

Author

Pontus von Brömssen, Sep 09 2023

Keywords

Crossrefs

Cf. A096267 (2 dimensions), A365559 (free), A365562 (4 dimensions), A365564 (5 dimensions).
14th row of A366767.

Extensions

a(9)-a(12) from John Mason, Mar 06 2025
a(13) from John Mason, Mar 23 2025
a(14)-a(18) from Mertens & Moore added by Andrei Zabolotskii, Jun 27 2025

A365562 Number of fixed n-polysticks (or polyedges) in 4 dimensions.

Original entry on oeis.org

4, 28, 252, 2600, 29248, 349132, 4351944, 56062681, 741132648, 10003860384, 137367013012, 1913480724898, 26980497086268, 384428067086544, 5527398761722192
Offset: 1

Views

Author

Pontus von Brömssen, Sep 09 2023

Keywords

Crossrefs

Cf. A096267 (2 dimensions), A365560 (3 dimensions), A365561 (free), A365564 (5 dimensions).
42nd row of A366767.

Extensions

a(8)-a(15) from Mertens and Moore (a(8)-a(12) computed from Appendix A, a(13)-a(15) from Table 1), added by Pontus von Brömssen, Jun 29 2025

A365655 Number of fixed n-polyominoids, allowing right-angled connections only ("hard" polyominoids).

Original entry on oeis.org

3, 12, 68, 438, 3054, 22417, 170610, 1334316
Offset: 1

Views

Author

Pontus von Brömssen, Sep 17 2023

Keywords

Comments

Apparently, the definition of "hard" polyominoid in the Wikipedia article differs from the definition used here. Here, two squares are allowed to meet in a straight 180-degree connection provided that the structure be connected through right-angled ("hard") connections only; see A365654 for further details.

Crossrefs

Cf. A075678 (polyominoids), A365654 (free).
13th and 17th row of A366767.
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