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 1-3 of 3 results.

A354492 Diagonal of A354703.

Original entry on oeis.org

1, 2, 2, 4, 4, 4, 9, 7, 9, 4, 9, 16, 7, 16, 8, 14, 9, 12, 23, 13, 21, 8, 17, 32, 20, 28
Offset: 1

Views

Author

Hugo Pfoertner, Jun 22 2022

Keywords

Comments

a(n)-n is an indicator of whether the free space between the covered grid points and the perimeter of the square is relatively large. a(n)-n > 0 for n = 7, 12, 14, 19, 24, 26, ... . A comparison with the linked illustrations from A354702 shows that in all these cases the covering square is rotated by Pi/4 and that the next outer diagonal rows of grid points are very close to the perimeter of the covering square.
In these cases it is favorable if the difference from n*sqrt(2) to the next larger integer is as small as possible. This also fits with 7 and 12 being terms in A084068. Since A084068(5) = 41, it is expected that a record of a(n)-n will occur at a(41) = 41^2 - A354702(41,41) = 1681 - 1624 = 57 and a(n)-n = 16.

Links

Crossrefs

Cf. A084068, A293330, A354702, A354703.
A354707 is the analogous sequence, but for the problem of maximizing the number of grid points covered.

A354702 T(w,h) is an upper bound for the minimum number of grid points in a square grid covered by an arbitrarily positioned and rotated rectangle of width w and height h, where T(w,h) is a triangle read by rows.

Original entry on oeis.org

0, 1, 2, 2, 4, 7, 2, 5, 9, 12, 3, 7, 13, 17, 21, 4, 8, 15, 20, 26, 32, 4, 9, 18, 22, 31, 36, 40, 5, 11, 20, 27, 36, 44, 49, 57, 6, 12, 24, 30, 41, 48, 54, 66, 72, 7, 14, 26, 35, 46, 55, 63, 74, 84, 96, 7, 15, 28, 37, 50, 60, 67, 81, 90, 105, 112, 8, 16, 31, 40, 55, 64, 72, 88, 96, 112, 120, 128
Offset: 1

Views

Author

Hugo Pfoertner, Jun 15 2022

Keywords

Comments

Grid points must lie strictly within the covering rectangle, i.e., grid points on the perimeter of the rectangle are not allowed.
These upper bounds were determined by an extensive random search, the results of which were stable. The proof that none of these bounds can be improved should be possible with a constructive technique such as integer linear programming applied to all combinatorially possible positions of the rectangle relative to the lattice.
A simple random search is implemented in the attached PARI program, which enables a plausibility check of the results for small covering rectangles. It also provides results for the maximum problem. Additional methods were used to obtain the results shown. In particular, angular orientations of the rectangle along connecting lines between all pairs of lattice points and extreme positions of the rectangle, where lattice points are very close to the corners of the rectangle, were investigated, using adjacent terms in A000404.

Examples

			The triangle begins:
    \ h 1   2   3   4   5   6   7   8   9   10   11   12
   w \ -------------------------------------------------
   1 |  0;  |   |   |   |   |   |   |   |    |    |    |
   2 |  1,  2;  |   |   |   |   |   |   |    |    |    |
   3 |  2,  4,  7;  |   |   |   |   |   |    |    |    |
   4 |  2,  5,  9, 12;  |   |   |   |   |    |    |    |
   5 |  3,  7, 13, 17, 21;  |   |   |   |    |    |    |
   6 |  4,  8, 15, 20, 26, 32;  |   |   |    |    |    |
   7 |  4,  9, 18, 22, 31, 36, 40;  |   |    |    |    |
   8 |  5, 11, 20, 27, 36, 44, 49, 57;  |    |    |    |
   9 |  6, 12, 24, 30, 41, 48, 54, 66, 72;   |    |    |
  10 |  7, 14, 26, 35, 46, 55, 63, 74, 84,  96;   |    |
  11 |  7, 15, 28, 37, 50, 60, 67, 81, 90, 105, 112;   |
  12 |  8, 16, 31, 40, 55, 64, 72, 88, 96, 112, 120, 128

Links

Crossrefs

Cf. A293330 (diagonal).
Cf. A354492, A354703, A354704, A354705, A355241, A355242.
Cf. A291259 (similar problem for circular disks).
Cf. A000404 (used to check extreme positions of grid points).

Programs

  • PARI
    \\ See link.
  • PARI
    \\ See also program link in A355241.

A354705 T(w,h) = (w+1)*(h+1) - A354704(w,h) is an upper bound for the deficit in the number of grid points covered by an optimally positioned and rotated cover compared to the excluded singular case of an axis-parallel, unshifted cover, where T(w,h) and A354704 are triangles read by rows.

Original entry on oeis.org

2, 3, 4, 3, 4, 3, 4, 5, 5, 7, 4, 6, 4, 6, 4, 5, 7, 5, 8, 6, 8, 6, 7, 7, 10, 8, 11, 11, 6, 8, 6, 9, 6, 9, 12, 9, 7, 9, 7, 11, 8, 11, 12, 12, 11, 7, 10, 6, 10, 6, 9, 13, 9, 12, 8, 8, 11, 8, 12, 8, 12, 15, 12, 15, 12, 16, 9, 11, 9, 13, 10, 14, 16, 15, 16, 15, 19, 20
Offset: 1

Views

Author

Hugo Pfoertner, Jun 15 2022

Keywords

Comments

See A354707 for an interpretation of the diagonal terms.

Examples

			The triangle begins:
    \ h 1   2  3   4   5   6   7   8   9  10  11  12
   w \ ---------------------------------------------
   1 |  2;  |  |   |   |   |   |   |   |   |   |   |
   2 |  3,  4; |   |   |   |   |   |   |   |   |   |
   3 |  3,  4, 3;  |   |   |   |   |   |   |   |   |
   4 |  4,  5, 5,  7;  |   |   |   |   |   |   |   |
   5 |  4,  6, 4,  6,  4;  |   |   |   |   |   |   |
   6 |  5,  7, 5,  8,  6,  8;  |   |   |   |   |   |
   7 |  6,  7, 7, 10,  8, 11, 11;  |   |   |   |   |
   8 |  6,  8, 6,  9,  6,  9, 12,  9;  |   |   |   |
   9 |  7,  9, 7, 11,  8, 11, 12, 12, 11;  |   |   |
  10 |  7, 10, 6, 10,  6,  9, 13,  9, 12,  8;  |   |
  11 |  8, 11, 8, 12,  8, 12, 15, 12, 15, 12, 16;  |
  12 |  9, 11, 9, 13, 10, 14, 16, 15, 16, 15, 19, 20

Links

Crossrefs

Cf. A354707 (diagonal).
Cf. A354702, A354703 (similar, but for minimizing the number of covered points), A354704.
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement.