A366766 -id:A366766 - cp's OEIS frontend

A366768 Array read by antidiagonals, where each row is the coordination sequence for the underlying graph of the polyominoids occurring in the corresponding row of A366766.

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, 8, 6, 1, 0, 2, 0, 2, 12, 16, 0, 1, 0, 2, 0, 2, 16, 24, 0, 4, 1, 0, 2, 0, 2, 20, 32, 0, 8, 4, 1, 0, 2, 0, 2, 24, 40, 0, 12, 8, 8, 1, 0, 2, 0, 2, 28, 48, 0, 16, 12, 16, 0, 1

Offset: 1

Pontus von Brömssen, Oct 22 2023

The underlying graph of a given type of polyominoids has all possible cells as nodes and edges between cells that are connected (respecting which types of connections are allowed). See A366766 for details on how the allowed connections are specified and on the ordering of the rows.

			Array begins:
  n\k| 0  1  2   3   4   5   6   7   8   9   10   11
  ---+----------------------------------------------
   1 | 1  0  0   0   0   0   0   0   0   0    0    0
   2 | 1  2  2   2   2   2   2   2   2   2    2    2
   3 | 1  0  0   0   0   0   0   0   0   0    0    0
   4 | 1  2  2   2   2   2   2   2   2   2    2    2
   5 | 1  4  8  12  16  20  24  28  32  36   40   44
   6 | 1  6 16  24  32  40  48  56  64  72   80   88
   7 | 1  0  0   0   0   0   0   0   0   0    0    0
   8 | 1  4  8  12  16  20  24  28  32  36   40   44
   9 | 1  4  8  12  16  20  24  28  32  36   40   44
  10 | 1  8 16  24  32  40  48  56  64  72   80   88
  11 | 1  0  0   0   0   0   0   0   0   0    0    0
  12 | 1  2  2   2   2   2   2   2   2   2    2    2
  13 | 1  8 30  68 126 180 286 348 510 572  798  852
  14 | 1 10 46 106 190 298 430 586 766 970 1198 1450
  15 | 1  0  0   0   0   0   0   0   0   0    0    0
  16 | 1  4  8  12  16  20  24  28  32  36   40   44
  17 | 1  8 30  68 126 180 286 348 510 572  798  852
  18 | 1 12 50 110 194 302 434 590 770 974 1202 1454

Pontus von Brömssen, Python programs that relate row numbers and parameter sets.
Wikipedia, Polyominoid.
Index entries for coordination sequences.
Index entries for sequences related to polyominoes.

Cf. A366766, A366767.

A000105 Number of free polyominoes (or square animals) with n cells.

Original entry on oeis.org

1, 1, 1, 2, 5, 12, 35, 108, 369, 1285, 4655, 17073, 63600, 238591, 901971, 3426576, 13079255, 50107909, 192622052, 742624232, 2870671950, 11123060678, 43191857688, 168047007728, 654999700403, 2557227044764, 9999088822075, 39153010938487, 153511100594603

Offset: 0

N. J. A. Sloane

For n>0, a(n) + A030228(n) = A000988(n) because the number of free polyominoes plus the number of polyominoes lacking bilateral symmetry equals the number of one-sided polyominoes. - Graeme McRae, Jan 05 2006
The possible symmetry groups of a (nonempty) polyomino are the 10 subgroups of the dihedral group D_8 of order 8: D_8, 1, Z_2 (five times), Z_4, (Z_2)^2 (twice). - Benoit Jubin, Dec 30 2008
Names for first few polyominoes: monomino, domino, tromino, tetromino, pentomino, hexomino, heptomino, octomino, enneomino, decomino, hendecomino, dodecomino, ...
Limit_{n->oo} a(n)^(1/n) = mu with 3.98 < mu < 4.64 (quoted by Castiglione et al., with a reference to Barequet et al., 2006, for the lower bound). The upper bound is due to Klarner and Rivest, 1973. By Madras, 1999, it is now known that this limit, also known as Klarner's constant, is equal to the limit growth rate lim_{n->oo} a(n+1)/a(n).
Polyominoes are worth exploring in the elementary school classroom. Students in grade 2 can reproduce the first 6 terms. Grade 3 students can explore area and perimeter. Grade 4 students can talk about polyomino symmetries.
The pentominoes should be singled out for special attention: 1) they offer a nice, manageable set that a teacher can commercially acquire without too much expense. 2) There are also deeply strategic games and perplexing puzzles that are great for all students. 3) A fraction of students will become engaged because of the beautiful solutions.
Conjecture: Almost all polyominoes are holey. In other words, A000104(n)/a(n) tends to 0 for increasing n. - John Mason, Dec 11 2021 (This is true, a consequence of Madras's 1999 pattern theorem. - Johann Peters, Jan 06 2024)

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

S. W. Golomb, Polyominoes, Appendix D, p. 152; Princeton Univ. Pr. NJ 1994
J. E. Goodman and J. O'Rourke, editors, Handbook of Discrete and Computational Geometry, CRC Press, 1997, p. 229.
D. A. Klarner, The Mathematical Gardner, p. 252 Wadsworth Int. CA 1981
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.
George E. Martin, Polyominoes - A Guide to Puzzles and Problems in Tiling, The Mathematical Association of America, 1996
Ed Pegg, Jr., Polyform puzzles, in Tribute to a Mathemagician, Peters, 2005, pp. 119-125.
R. C. Read, Some applications of computers in graph theory, in L. W. Beineke and R. J. Wilson, editors, Selected Topics in Graph Theory, Academic Press, NY, 1978, pp. 417-444.
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).

John Mason, Table of n, a(n) for n = 0..50 (terms 0..45,47 from Toshihiro Shirakawa)
Z. Abel, E. Demaine, M. Demaine, H. Matsui and G. Rote, Common Developments of Several Different Orthogonal Boxes.
G. Barequet, M. Moffie, A. Ribo and G. Rote, Counting polyominoes on twisted cylinders, Integers 6 (2006), A22, 37 pp. (electronic).
K. S. Brown, Polyomino Enumerations
G. Castiglione, A. Frosini, E. Munarini, A. Restivo and S. Rinaldi, Combinatorial aspects of L-convex polyominoes, European J. Combin. 28 (2007), no. 6, 1724-1741.
Juris Čerņenoks and Andrejs Cibulis, Tetrads and their Counting, Baltic J. Modern Computing, Vol. 6 (2018), No. 2, 96-106.
A. Clarke, Polyominoes
A. R. Conway and A. J. Guttmann, On two-dimensional percolation, J. Phys. A: Math. Gen. 28(1995) 891-904.
I. Jensen, Enumerations of lattice animals and trees, arXiv:cond-mat/0007239 [cond-mat.stat-mech], 2000.
I. Jensen and A. J. Guttmann, Statistics of lattice animals (polyominoes) and polygons, Journal of Physics A: Mathematical and General, vol. 33, pp. L257-L263, 2000.
M. Keller, Counting polyforms.
D. A. Klarner and R. L. Rivest, A procedure for improving the upper bound for the number of n-ominoes, Canadian J. of Mathematics, 25 (1973), 585-602.
N. Madras, A pattern theorem for lattice clusters, arXiv:math/9902161 [math.PR], 1999; Annals of Combinatorics, 3 (1999), 357-384.
John Mason, Counting size 50 polyominoes -V2
S. Mertens, Lattice animals: a fast enumeration algorithm and new perimeter polynomials, J. Statistical Physics, vol. 58, no. 5/6, pp. 1095-1108, Mar. 1990.
Stephan Mertens and Markus E. Lautenbacher, Counting lattice animals: A parallel attack J. Stat. Phys., vol. 66, no. 1/2, pp. 669-678, 1992.
W. R. Muller, K. Szymanski, J. V. Knop, and N. Trinajstic, On the number of square-cell configurations, Theor. Chim. Acta 86 (1993) 269-278
Joseph Myers, Polyomino tiling
Tomás Oliveira e Silva, Animal enumerations on regular tilings in Spherical, Euclidean and Hyperbolic 2-dimensional spaces
Tomás Oliveira e Silva, Animal enumerations on the {4,4} Euclidean tiling [The enumeration to order 28]
T. R. Parkin, L. J. Lander, and D. R. Parkin, Polyomino Enumeration Results, presented at SIAM Fall Meeting, 1967, and accompanying letter from T. J. Lander (annotated scanned copy)
Anuj Pathania, Scalable Task Schedulers for Many-Core Architectures, Ph.D. Thesis, Karlsruher Instituts für Technologie (Germany, 2018).
Ed Pegg, Jr., Illustrations of polyforms
Henri Picciotto, Polyomino Lessons
Jaime Rangel-Mondragón, Polyominoes and Related Families, The Mathematica Journal, Volume 9, Issue 3.
D. H. Redelmeier, Counting polyominoes: yet another attack, Discrete Math., 36 (1981), 191-203.
D. H. Redelmeier, Table 3 of Counting polyominoes...
Toshihiro Shirakawa, Harmonic Magic Square, pp 3-4: Enumeration of Polyominoes considering the symmetry, April 2012.
Herman Tulleken, Polyominoes 2.2: How they fit together, (2019).
Eric Weisstein's World of Mathematics, Polyomino
Wikipedia, The 35 hexominoes
Wikipedia, The 108 heptominoes
Wikipedia, The 369 octominoes
Wikipedia, Polyomino
D. Xu, T. Horiyama, T. Shirakawa and R. Uehara, Common Developments of Three Incongruent Boxes of Area 30, in Proc. 12th Annual Conference, TAMC 2015, Singapore, May 18-20, 2015, LNCS Vol. 9076, pp. 236-247.
L. Zucca, Pentominoes
L. Zucca, The 12 pentominoes
Index entries for "core" sequences

Sequences classifying polyominoes by symmetry group: A006746, A006747, A006748, A006749, A056877, A056878, A142886, A144553, A144554.
Cf. A001168 (not reduced by D_8 symmetry), A000104 (no holes), A054359, A054360, A001419, A000988, A030228 (chiral polyominoes).
See A006765 for another version.
Cf. also A000577, A000228, A103465, A210996 (bisection).
Excluding a(0), 8th and 9th row of A366766.

(* In this program by Jaime Rangel-Mondragón, polyominoes are represented as a list of Gaussian integers. *)
polyominoQ[p_List] := And @@ ((IntegerQ[Re[#]] && IntegerQ[Im[#]])& /@ p);
rot[p_?polyominoQ] := I*p;
ref[p_?polyominoQ] := (# - 2 Re[#])& /@ p;
cyclic[p_] := Module[{i = p, ans = {p}}, While[(i = rot[i]) != p, AppendTo[ans, i]]; ans];
dihedral[p_?polyominoQ] := Flatten[{#, ref[#]}& /@ cyclic[p], 1];
canonical[p_?polyominoQ] := Union[(# - (Min[Re[p]] + Min[Im[p]]*I))& /@ p];
allPieces[p_] := Union[canonical /@ dihedral[p]];
polyominoes[1] = {{0}};
polyominoes[n_] := polyominoes[n] = Module[{f, fig, ans = {}}, fig = ((f = #1; ({f, #1 + 1, f, #1 + I, f, #1 - 1, f, #1 - I}&) /@ f)&) /@ polyominoes[n - 1]; fig = Partition[Flatten[fig], n]; f = Select[Union[canonical /@ fig], Length[#1] == n &]; While[f != {}, ans = {ans, First[f]}; f = Complement[f, allPieces[First[f]]]]; Partition[Flatten[ans], n]];
a[n_] := a[n] = Length[ polyominoes[n]];
Table[Print["a(", n, ") = ", a[n]]; a[n], {n, 1, 12}] (* Jean-François Alcover, Mar 24 2015, after Jaime Rangel-Mondragón *)

a(n) = A000104(n) + A001419(n). - R. J. Mathar, Jun 15 2014
a(n) = A006749(n) + A006746(n) + A006748(n) + A006747(n) + A056877(n) + A056878(n) + A144553(n) + A142886(n). - Andrew Howroyd, Dec 04 2018
a(n) = A259087(n) + A259088(n). - R. J. Mathar, May 22 2019
a(n) = (4*A006746(n) + 4*A006748(n) + 4*A006747(n) + 6*A056877(n) + 6*A056878(n) + 6*A144553(n) + 7*A142886(n) + A001168(n))/8. - John Mason, Nov 14 2021

Extended to n=28 by Tomás Oliveira e Silva
Link updated by William Rex Marshall, Dec 16 2009
Edited by Gill Barequet, May 24 2011
Misspelling "polyominos" corrected by Don Knuth, May 03 2016
a(29)-a(45), a(47) from Toshihiro Shirakawa
a(46) calculated using values from A001168 (I. Jensen), A006748/A056877/A056878/A144553/A142886 (Robert A. Russell) and A006746/A006747 (John Mason), Nov 14 2021

A038119 Number of n-celled solid polyominoes (or free polycubes, allowing mirror-image identification).

Original entry on oeis.org

1, 1, 2, 7, 23, 112, 607, 3811, 25413, 178083, 1279537, 9371094, 69513546, 520878101, 3934285874, 29915913663, 228779330204, 1758309223457, 13573319825615, 105192814197984, 818136047201932, 6383528588447574

Offset: 1

N. J. A. Sloane

a(1)-a(12) computed by Achim Flammenkamp.
A000162 but with one copy of each mirror-image deleted.
From R. J. Mathar, Mar 19 2018: (Start)
We can split the numbers into an irregular table which lists in row n how many configurations have c contacts for c >= 0:
  1;
  0 1;
  0 0 2;
  0 0 0 6 1;
  0 0 0 0 21 2;
  0 0 0 0 0 91 19 2;
  0 0 0 0 0 0 484 110 12 1;
  0 0 0 0 0 0 0 2817 852 129 12 0 1;
  0 0 0 0 0 0 0 0 17788 6321 1166 132 5 1;
Row lengths are 1+A007818(n). Row sums are a(n).
(End)
Number of unoriented polyominoes with n cubical cells of the regular tiling with Schläfli symbol {4,3,4}. For unoriented polyominoes, chiral pairs are counted as one.- Robert A. Russell, Mar 21 2024

S. W. Golomb, Polyominoes. Scribner's, NY, 1965; second edition (Polyominoes: Puzzles, Packings, Problems and Patterns) Princeton Univ. Press, 1994.
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. [See https://books.google.nl/books?id=ja7iBQAAQBAJ&pg=PA101]
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Achim Flammenkamp, Home page.
Kevin L. Gong, Polyominoes Home Page.
John Mason, Counting free polycubes.
John Mason, Coordinate sets of examples of polycube symmetry (version 2)

A038119 = (A007743+A000162)/2, A007743 = 2*A038119 - A000162, A000162 = 2*A038119 - A007743.
32nd row of A366766.
Cf. A000162 (oriented), A371397 (chiral), A007743 (achiral), A001931 (fixed).
Cf. for each symmetry: A376964, A376965, A376966, A376967, A376968, A376969, A376970, A376972, A376973, A376974, A376975, A376976, A376977, A376978, A376979, A376980, A376981, A376982, A376983, A377127, A376984, A376985, A376986, A376987, A376988, A376989, A377128, A376990, A376991, A377129, A377130, A377131, A376971

A[s_Integer] := With[{s6 = StringPadLeft[ToString[s], 6, "0"]}, Cases[ Import["https://oeis.org/A" <> s6 <> "/b" <> s6 <> ".txt", "Table"], {, }][[All, 2]]];
A000162 = A@000162;
A007743 = A@007743;
a[n_] := (A007743[[n]] + A000162[[n]])/2;
a /@ Range[16] (* Jean-François Alcover, Jan 16 2020 *)

a(n) = A000162(n) - A371397(n) = A371397(n) + A007743(n). - Robert A. Russell, Mar 21 2024

More terms from Brendan Owen (brendan_owen(AT)yahoo.com), Jan 02 2002
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), May 05 2007
More terms from John Mason, Sep 19 2024

A019988 Number of ways of embedding a connected graph with n edges in the square lattice.

Original entry on oeis.org

1, 2, 5, 16, 55, 222, 950, 4265, 19591, 91678, 434005, 2073783, 9979772, 48315186, 235088794, 1148891118, 5636168859, 27743309673

Offset: 1

Russ Cox

It is assumed that all edges have length one. - N. J. A. Sloane, Apr 17 2019
These are referred to as 'polysticks', 'polyedges' or 'polyforms'. - Jack W Grahl, Jul 24 2018
Number of connected subgraphs of the square lattice (or grid) containing n length-one line segments. Configurations differing only a rotation or reflection are not counted as different. The question may also be stated in terms of placing unit toothpicks in a connected arrangement on the square lattice. - N. J. A. Sloane, Apr 17 2019
The solution for n=5 features in the card game Digit. - Paweł Rafał Bieliński, Apr 17 2019

Brian R. Barwell, "Polysticks," Journal of Recreational Mathematics, 22 (1990), 165-175.

D. Goodger, An introduction to Polysticks
M. Keller, Counting polyforms
D. Knuth, Dancing Links, arXiv:cs/0011047 [cs.DS], 2000. (A discussion of backtracking algorithms which mentions some problems of polystick tiling.)
Ed Pegg, Jr., Illustrations of polyforms
N. J. A. Sloane, Illustration of a(1)-a(4)
Eric Weisstein's World of Mathematics, Polyedge
Wikicommons, Polysticks 5-sticks 6-sticks 7-sticks

If only translations (but not rotations) are factored, consider fixed polyedges (A096267).
If reflections are considered different, we obtain the one-sided polysticks, counted by (A151537). - Jack W Grahl, Jul 24 2018
Cf. A001997, A003792, A006372, A059103, A085632, A056841 (tree-like), A348095 (with cycles), A348096 (refined by symmetry), A181528.
See A336281 for another version.
6th row of A366766.

A348095(n) + A056841(n+1) = a(n). - R. J. Mathar, Sep 30 2021

More terms from Brendan Owen (brendan_owen(AT)yahoo.com), Feb 20 2002

a(18) from John Mason, Jun 01 2023

A366767 Array read by antidiagonals, where each row is the counting sequence of a certain type of fixed polyominoids.

Original entry on oeis.org

1, 0, 1, 0, 1, 2, 0, 1, 0, 2, 0, 1, 0, 2, 2, 0, 1, 0, 2, 4, 2, 0, 1, 0, 2, 12, 6, 1, 0, 1, 0, 2, 38, 22, 0, 1, 0, 1, 0, 2, 126, 88, 0, 2, 1, 0, 1, 0, 2, 432, 372, 0, 6, 2, 1, 0, 1, 0, 2, 1520, 1628, 0, 19, 6, 4, 3, 0, 1, 0, 2, 5450, 7312, 0, 63, 19, 20, 0, 3

Offset: 1

Pontus von Brömssen, Oct 22 2023

See A366766 (corresponding array for free polyominoids) for details.

			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 | 2  0  0   0   0    0     0      0      0       0        0         0
   4 | 2  2  2   2   2    2     2      2      2       2        2         2
   5 | 2  4 12  38 126  432  1520   5450  19820   72892   270536   1011722
   6 | 2  6 22  88 372 1628  7312  33466 155446  730534  3466170  16576874
   7 | 1  0  0   0   0    0     0      0      0       0        0         0
   8 | 1  2  6  19  63  216   760   2725   9910   36446   135268    505861
   9 | 1  2  6  19  63  216   760   2725   9910   36446   135268    505861
  10 | 1  4 20 110 638 3832 23592 147941 940982 6053180 39299408 257105146
  11 | 3  0  0   0   0    0     0      0      0       0        0         0
  12 | 3  3  3   3   3    3     3      3      3       3        3         3

Pontus von Brömssen, Python programs that relate row numbers and parameter sets.
Wikipedia, Polyominoid.
Index entries for sequences related to polyominoes.

Cf. A366766 (free), A366768.
The following table lists some sequences that are rows of the array, together with the corresponding values of D, d, and C (see A366766). 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:112223   |
    n | D | d |  h:010120   | sequence
  ----+---+---+-------------+----------
| 1 | 1 |  * -.....   | A063524
| 1 | 1 |  * X.....   | A000012
|!2 | 1 |  * --....   | 2*A063524
|!2 | 1 |    X-....   | 2*A000012
| 2 | 1 |    -X....   | 2*A001168
| 2 | 1 |  * XX....   | A096267
| 2 | 2 |  * -.-...   | A063524
| 2 | 2 |  * X.-...   | A001168
| 2 | 2 |  * -.X...   | A001168
| 2 | 2 |  * X.X...   | A006770
|!3 | 1 |  * --....   | 3*A063524
|!3 | 1 |    X-....   | 3*A000012
| 3 | 1 |    -X....   | A365655
| 3 | 1 |  * XX....   | A365560
|!3 | 2 |  * ----..   | 3*A063524
|!3 | 2 |    X---..   | 3*A001168
| 3 | 2 |    -X--..   | A365655
| 3 | 2 |  * XX--..   | A075678
|!3 | 2 |    --X-..   | 3*A001168
|!3 | 2 |    X-X-..   | 3*A006770
| 3 | 2 |    -XX-..   | A365996
| 3 | 2 |    XXX-..   | A365998
| 3 | 2 |    ---X..   | A366000
| 3 | 2 |    X--X..   | A366002
| 3 | 2 |    -X-X..   | A366004
| 3 | 2 |    XX-X..   | A366006
| 3 | 2 |  * --XX..   | A365653
| 3 | 2 |    X-XX..   | A366008
| 3 | 2 |    -XXX..   | A366010
| 3 | 2 |  * XXXX..   | A365651
| 3 | 3 |  * -.-..-   | A063524
| 3 | 3 |  * X.-..-   | A001931
| 3 | 3 |  * -.X..-   | A039742
| 3 | 3 |  * X.X..-   |
| 3 | 3 |  * -.-..X   | A039741
| 3 | 3 |  * X.-..X   |
| 3 | 3 |  * -.X..X   |
| 3 | 3 |  * X.X..X   |
|!4 | 1 |  * --....   | 4*A063524
|!4 | 1 |    X-....   | 4*A000012
| 4 | 1 |    -X....   | A366341
| 4 | 1 |  * XX....   | A365562
|!4 | 2 |  * -----.   | 6*A063524
|!4 | 2 |    X----.   | 6*A001168
| 4 | 2 |    -X---.   | A366339
| 4 | 2 |  * XX---.   | A366335
|!4 | 2 |    --X--.   | 6*A001168
|!4 | 2 |    X-X--.   | 6*A006770

A038173 Number of "connected animals" formed from n rhombic dodecahedra (or edge-connected cubes) in the face-centered cubic lattice, allowing translation and rotations of the lattice and reflections.

Original entry on oeis.org

1, 1, 4, 20, 131, 1211, 12734, 144158, 1687737, 20196788, 245366931, 3016835487

Offset: 1

Achim Flammenkamp

This extends earlier work of Torsten Sillke (torsten.sillke(AT)lhsystems.com).

S. T. Coffin, Puzzling World of Polyhedral Dissections, Oxford Univ. Press, 1991.
George Sicherman, Catalogue of Polyrhons
T. Sillke, Notations for polyspheres
Index entries for sequences related to f.c.c. lattice

Cf. A000162, A038119 (for simple-cubic lattice), A038168-A038174, A300812 (refined by number of contacts).

33rd row of A366766.

a(10) from George Sicherman, Jul 24 2012
a(11) from Joerg Arndt and Márk Péter Légrádi, Apr 30 2023
a(12) from Bert Dobbelaere, Jun 26 2025

A365654 Number of free n-polyominoids, allowing right-angled connections only ("hard" polyominoids).

Original entry on oeis.org

1, 1, 5, 16, 90, 537, 3826, 28655, 225534

Offset: 1

Pontus von Brömssen, Sep 17 2023

Two squares are allowed to meet in a straight 180-degree connection, but the structure must be connected through right-angled ("hard") connections only. This seems to be in agreement with the definition of "hard" polyominoids in the Mireles Jasso link (the number of fixed hard hexominoids given by the "sample report" linked from that web-page agrees with A365655(6) = 22417), but differs from the definition in the Wikipedia article. The smallest example of a polyominoid that is included here but is not hard according to Wikipedia consists of two squares between (0,0,1) and (2,1,1), two between (0,0,1) and (2,0,2), and one between (1,0,0) and (1,1,1) (a "one-legged sofa", see illustration in the Mireles Jasso link). This explains why a(5) = 90, while the number of hard pentominoids is 89 according to the Wikipedia article.
Equivalently, number of n-polysticks in 3 dimensions, connected through right-angled connections.
Also, the number of face-connected polyhedral components in the square bipyramidal honeycomb up to translation, rotation, and reflection of the honeycomb. - Peter Kagey, Jun 10 2025

Pontus von Brömssen, Illustration for sizes 1..4.
Peter Kagey, Animated illustration of the a(4)=16 free polyforms on the square bipyramidal honeycomb.
Jorge Luis Mireles Jasso, The Polyominoids.
Wikipedia, Polyominoid.
Wikipedia, Polystick.
Index entries for sequences related to polyominoes.

13th and 17th row of A366766.

Cf. A075679 (polyominoids), A365559 (polysticks in 3 dimensions), A365655 (fixed).

a(9) from Pontus von Brömssen, Mar 03 2025

cp's OEIS Frontend

A366768 Array read by antidiagonals, where each row is the coordination sequence for the underlying graph of the polyominoids occurring in the corresponding row of A366766.

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A000105 Number of free polyominoes (or square animals) with n cells.

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A038119 Number of n-celled solid polyominoes (or free polycubes, allowing mirror-image identification).

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A019988 Number of ways of embedding a connected graph with n edges in the square lattice.

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A366767 Array read by antidiagonals, where each row is the counting sequence of a certain type of fixed polyominoids.

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A038173 Number of "connected animals" formed from n rhombic dodecahedra (or edge-connected cubes) in the face-centered cubic lattice, allowing translation and rotations of the lattice and reflections.

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A365654 Number of free n-polyominoids, allowing right-angled connections only ("hard" polyominoids).

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A068870 Number of polyhypercubes or 4-dimensional polyominoes with n cells (regarding mirror-images as identical).

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A030222 Number of n-polyplets (polyominoes connected at edges or corners); may contain holes.

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