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 1-6 of 6 results.

A350408 Erroneous version of A187015.

Original entry on oeis.org

1, 2, 3, 7, 6, 13, 11, 27
Offset: 1

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Keywords

A322345 Maximal number of vertices of a convex lattice polygon containing n lattice points in its interior.

Original entry on oeis.org

4, 6, 6, 6, 8, 7, 8, 9, 8, 8, 10, 9, 9, 10, 10, 10, 10, 11, 10, 12, 12, 12, 11, 11, 12, 12, 12, 13, 12, 12, 13, 13, 13, 13, 14, 14, 13, 13, 14, 14, 14, 14, 14, 14, 14, 15, 14, 15, 15, 15, 15, 15, 16, 15, 16, 15, 16, 16, 15, 15, 16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 16, 17, 17, 16, 17, 17
Offset: 0

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Author

Hugo Pfoertner, Dec 04 2018

Keywords

Comments

This is an inverse of A063984 in the following sense: A063984(k) = min {n : a(n)>=k}. Thus a(n) grows roughly like const*n^(1/3). - Günter Rote, Sep 19 2023

Crossrefs

Programs

  • Python
    # See the Python program in the links section.

Extensions

a(0) added by Andrey Zabolotskiy, Dec 29 2021
Name clarified by Günter Rote, Sep 18 2023
a(31) onwards from Günter Rote, Oct 01 2023

A371917 Number of inequivalent convex lattice polygons containing n lattice points (including points on the boundary).

Original entry on oeis.org

1, 3, 6, 13, 21, 41, 67, 111, 175, 286, 419, 643, 938, 1370, 1939, 2779, 3819, 5293, 7191, 9752, 12991, 17321, 22641, 29687, 38533, 49796, 63621, 81300, 102807, 129787, 162833, 203642, 252898, 313666, 386601, 475540, 582216, 710688, 863552, 1048176
Offset: 3

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Author

Justus Springer, Apr 12 2024

Keywords

Comments

A322343 counts the polygons by their number of interior lattice points, excluding points on the boundary.

Examples

			For n = 3, the only polygon is the standard triangle with vertices (0,0), (1,0) and (0,1).
For n = 4, a(4) = 3 and the three polygons have vertex sets {(1,0),(0,1),(-1,-1)}, {(0,0),(2,0),(0,1)} and {(0,0),(1,0),(0,1),(1,1)}.
		

Crossrefs

A366409 Number of smooth convex lattice polygons with area n/2.

Original entry on oeis.org

1, 1, 1, 3, 2, 4, 4, 6, 5, 7, 7, 9, 7, 12, 12, 15, 9, 15, 16, 18, 13, 23, 21, 24, 19, 26, 25, 30, 22, 39, 34, 34, 27, 46, 42, 41, 35, 60, 53, 56, 41, 63, 61, 62, 61, 91, 66, 72, 78, 111, 87, 86, 83, 135, 123, 111, 97, 142, 135, 156, 146, 176, 148, 186, 194, 206, 169, 200, 242, 313
Offset: 1

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Author

Günter Rote, Oct 09 2023

Keywords

Comments

A lattice polygon is a polygon whose vertices have integer coordinates. (They belong to the integer lattice or grid Z x Z).
A convex lattice polygon is smooth if, for every vertex V, the adjacent lattice points on the two incident edges (which are not necessarily vertices) form together with V a triangle of area 1/2.

Examples

			Here is a smooth lattice polygon with k=6 vertices (V), 2 lattice points on edges (B), 2 interior lattice points (I), and area 5, shown as part of the grid: (The edges of the polygon are not drawn.)
     V--V--+--+--+
     |  |  |  |  |
     V--I--B--+--+
     |  |  |  |  |
     +--V--I--B--+
     |  |  |  |  |
     +--+--+--V--V
See Bogart et al., Theorem 32, and Appendix, p. 325, for a list of all 41 (convex) smooth lattice polygons with at most 12 lattice points, with figures.
The dataset of Balletti gives the complete set of 1530 polygons up to area 25. Beware that the vertices are not always listed in sorted (clockwise or counterclockwise) order around the polygon boundary.
		

Crossrefs

Cf. A187015 for lattice polygons without the smoothness restriction. Cf. A127709.

Programs

  • Python
    # See the links section.

A374975 Number of equivalence classes of lattice polygons contained in a square of side length n but not in a square of side length n-1.

Original entry on oeis.org

2, 15, 131, 1369, 13842, 129185, 1104895, 8750964, 64714465, 450686225, 2976189422
Offset: 1

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Author

Justus Springer, Jul 26 2024

Keywords

Examples

			For n = 1, only the square itself and the standard triangle are contained in the square, so a(1) = 2.
		

Crossrefs

A377245 Number of equivalence classes of convex lattice polygons containing n lattice points, restricting the count to those polygons that are interior to another polygon.

Original entry on oeis.org

1, 3, 4, 5, 7, 11, 16, 21, 25, 37, 46, 60, 69, 95, 110, 146, 179, 218, 258, 328, 378, 480, 557, 680, 792, 965, 1090, 1320, 1549, 1814, 2091, 2487, 2839, 3360, 3809, 4406, 5062, 5893, 6594, 7642, 8705, 9955, 11254, 12852, 14395, 16556, 18588, 20894, 23535
Offset: 3

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Author

Justus Springer, Oct 21 2024

Keywords

Comments

See Castryck article for an explanation how to check if a polygon is interior to another polygon by application of theorem 5 (Koelman 1991).
The polygons up to 112 lattice points can be downloaded from the zenodo dataset linked below.

Crossrefs

Showing 1-6 of 6 results.