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.

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A071333 Number of polyiamonds with n cells that do not tile the plane.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 1, 0, 21, 107, 619, 1300, 6740, 19812, 61075, 181036, 577551, 1626183, 4904626, 14071461, 41336066, 120630534, 352200161, 1023454347, 2997105957, 8761810505, 25648786717, 75161609591, 220583137840, 647825855933
Offset: 1

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Author

Joseph Myers, May 19 2002

Keywords

References

  • M. Gardner, Tiling with Polyominoes, Polyiamonds and Polyhexes. Chap. 14 in Time Travel and Other Mathematical Bewilderments. New York: W. H. Freeman, pp. 175-187, 1988.

Crossrefs

Equals A000577(n)-A071332(n) and A070764(n)+A071334(n). Cf. A054360, A070767.

Programs

  • Mathematica
    A[s_Integer] := With[{s6 = StringPadLeft[ToString[s], 6, "0"]}, Cases[ Import["https://oeis.org/A" <> s6 <> "/b" <> s6 <> ".txt", "Table"], {, }][[All, 2]]];
    A000577 = A@000577;
    A071332 = A@071332;
    a[n_] := A000577[[n]] - A071332[[n]];
    a /@ Range[30] (* Jean-François Alcover, Feb 21 2020 *)

Extensions

More terms from Joseph Myers, Nov 11 2003
a(29) and a(30) from Joseph Myers, Nov 21 2010

A119602 Number of nonisomorphic polytetrahedra with n identical regular tetrahedra connected face-to-face or edge-to-edge (chiral shapes counted twice).

Original entry on oeis.org

1, 1, 2, 7, 39
Offset: 0

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Author

Jonathan Vos Post, Jun 02 2006

Keywords

Comments

Polytetrahedra are a 3-dimensional generalization of polyiamonds, composed of unit regular tetrahedra in Euclidean 3-space. - Peter Kagey, Aug 05 2019, adapted from comment by Jonathan Vos Post.

Examples

			For n = 1, the a(1) = 1 polytetrahedron is the tetrahedron itself.
For n = 2, the a(2) = 2 polytetrahedra are formed by either gluing two tetrahedra along a face (triangular bipyramid) or gluing two tetrahedra along an edge.
For n = 7, the a(3) = 7 polytetrahedra are given in the links section.
		

Crossrefs

A332930 Number of polyominoes with n cells on the order-6 square tiling of the hyperbolic plane.

Original entry on oeis.org

1, 1, 1, 2, 5, 16, 60, 255, 1193, 5862, 29875, 155995, 830539, 4489352, 24581675
Offset: 0

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Author

Peter Kagey, Mar 02 2020

Keywords

Comments

The order-6 square tiling has Schläfli symbol {4,6}.
This sequence is computed from via program by Christian Sievers in the Code Golf Stack Exchange link.

Crossrefs

Analogs with different Schläfli symbols are A000105 ({4,4}), A000207 ({3,oo}), A000577 ({3,6}), A005036 ({4,oo}), A119611 ({4,5}), and A330659 ({3,7}).

Extensions

a(9)-a(14) from Ed Wynn, Feb 16 2021

A359689 a(n) is the number of free polyiamonds of n cells with chessboard coloring.

Original entry on oeis.org

2, 1, 2, 4, 8, 19, 48, 120, 320, 864, 2372, 6581, 18470, 52094, 147966, 421931, 1208214, 3470789, 10001186, 28892674, 83671476, 242823392, 706090582, 2056861981, 6001601254, 17538308071, 51323923796, 150389970179, 441211039118, 1295886198194, 3810209524640, 11214075937205, 33035791339150
Offset: 1

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Author

John Mason, Jan 11 2023

Keywords

Crossrefs

Formula

See link "Counting Polyiamonds".

Extensions

More terms from John Mason, Oct 28 2023

A369365 Number of free rooted (or pointed) polyiamonds with n cells.

Original entry on oeis.org

1, 1, 2, 6, 16, 50, 150, 458, 1388, 4233, 12875, 39227, 119456, 363868, 1107912, 3372793, 10264156, 31228969
Offset: 1

Views

Author

Pontus von Brömssen, Jan 22 2024

Keywords

Crossrefs

Extensions

a(18) from John Mason, Sep 20 2024

A369367 Number of free n-celled polyiamonds with the least number (A369366(n)) of inequivalent cells.

Original entry on oeis.org

1, 1, 1, 3, 2, 1, 1, 1, 1, 4, 27, 1, 1, 6, 2, 1, 523, 1
Offset: 1

Views

Author

Pontus von Brömssen, Jan 22 2024

Keywords

Crossrefs

Extensions

a(18) from John Mason, Sep 20 2024

A385265 Number of edge-connected components of polygonal cells in the pinwheel tiling up to rotation of the tiling.

Original entry on oeis.org

1, 2, 4, 13, 53, 209, 904, 3963, 17900, 81745, 378554, 1768236, 8327789, 39471091, 188145066, 901117082, 4334151970, 20923370406, 101341800704, 492289834345
Offset: 0

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Author

Peter Kagey and Bert Dobbelaere, Jun 23 2025

Keywords

Comments

These are "one-sided" polyforms because there are no reflectional symmetries of the pinwheel tiling.
Here the "pinwheel tiling" is a tiling consisting of rectangular and square cells, and does not refer to non-periodic triangular tilings.

Crossrefs

A000105 (square), A000228 (hexagonal), A000577 (triangular), A197156 (prismatic pentagonal), A197159 (floret pentagonal), A197459 (rhombille), A197462 (kisrhombille), A197465 (tetrakis square), A309159 (snub square), A343398 (trihexagonal), A343406 (truncated hexagonal), A343577 (truncated square), A344211 (rhombitrihexagonal), A344213 (truncated trihexagonal), A383908 (snub trihexagonal), A385266 (basketweave).

A385266 Number of edge-connected components of polygonal cells in the basketweave tiling up to rotation and reflection of the tiling.

Original entry on oeis.org

1, 2, 2, 10, 34, 166, 777, 4053, 21225, 114594, 624242, 3442399, 19121661, 106964679, 601639326, 3400619170, 19301719485, 109962791254
Offset: 0

Views

Author

Peter Kagey and Bert Dobbelaere, Jun 23 2025

Keywords

Comments

Each square cell in the basketweave tiling is edge-connected to four rectangular cells.

Crossrefs

A000105 (square), A000228 (hexagonal), A000577 (triangular), A197156 (prismatic pentagonal), A197159 (floret pentagonal), A197459 (rhombille), A197462 (kisrhombille), A197465 (tetrakis square), A309159 (snub square), A343398 (trihexagonal), A343406 (truncated hexagonal), A343577 (truncated square), A344211 (rhombitrihexagonal), A344213 (truncated trihexagonal), A383908 (snub trihexagonal), A385265 (pinwheel).

A096361 Total number of triangles in all polyiamonds with n triangles.

Original entry on oeis.org

1, 2, 3, 12, 20, 72, 168, 528, 1440, 4480, 13046, 40008, 120055, 366324, 1109745, 3380752, 10269819, 31253904, 95011267, 288979680, 878550498, 2671223720, 8120041693, 24682865208, 75020015675, 227999634772, 692872971246, 2105464666676
Offset: 1

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Author

N. J. A. Sloane, Aug 04 2004

Keywords

Crossrefs

a(n) = n*A000577(n).

A130867 Triangular polyominoes (or polyiamonds) with n cells at most (turning over is allowed, holes are allowed, must be connected along edges).

Original entry on oeis.org

1, 2, 3, 6, 10, 22, 46, 112, 272, 720, 1906, 5240, 14475, 40641, 114624, 325921, 930028, 2666356, 7666949, 22115933, 63951671, 185370931, 538416222, 1566868939, 4567669566, 13336886288, 38998848186, 114194014853
Offset: 1

Views

Author

Tanya Khovanova, Jul 23 2007

Keywords

Crossrefs

Partial sums of A000577.
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