A333025 -id:A333025 - cp's OEIS frontend

A332953 The number of regions formed inside an isosceles triangle by straight line segments mutually connecting all vertices and all points that divide the two equal length sides into n equal parts; the base of the triangle contains no points other than its vertices.

1, 5, 18, 52, 125, 257, 486, 832, 1333, 2027, 3048, 4304, 6057, 8167, 10749, 13929, 18058, 22664, 28533, 34981, 42519, 51425, 62118, 73473, 86768, 101902, 118695, 137138, 159147, 181752, 208813, 237209, 268614, 303718, 340882, 380811, 427540, 477134, 530047

Offset: 1

Scott R. Shannon and N. J. A. Sloane, Mar 04 2020

nonn

The terms are from numeric computation - no formula for a(n) is currently known.
Equivalently, this is also the number of regions formed when all the integer points along the x and y axes with 0 <= x <= n and 0 <= y <= n are joined by straight line segments.
If instead one takes points on the x and y axes with coordinates 1, 1/2, 1/3, 1/4, ..., 1/n, 0, and joins them all by line segments, the resulting figure contains only triangles and quadrilaterals, and the number of regions is given by A332358 (and more generally by A332357 if there are m+1 such points on the x axis and n+1 such points on the y axis).

Lars Blomberg, Table of n, a(n) for n = 1..70
Scott R. Shannon, Illustration for n = 2.
Scott R. Shannon, Illustration for n = 3.
Scott R. Shannon, Illustration for n = 4.
Scott R. Shannon, Illustration for n = 5.
Scott R. Shannon, Illustration for n = 6.
Scott R. Shannon, Illustration for n = 8.
Scott R. Shannon, Illustration for n = 10.
Scott R. Shannon, Illustration for n = 12.
Scott R. Shannon, Illustration for n = 15.
Scott R. Shannon, Illustration for n = 5 with random distance-based coloring.
Scott R. Shannon, Illustration for n = 10 with random distance-based coloring.
Scott R. Shannon, Illustration for n = 15 with random distance-based coloring.

Cf. A333025 (n-gons), A333026 (vertices), A333027 (edges), A007678, A092867, A331452, A331911, A332357, A332358.

a(16) and beyond from Lars Blomberg, May 26 2020

A333027 The number of edges formed on an isosceles triangle by straight line segments mutually connecting all vertices and all points that divide the two equal length sides into n equal parts; the base of the triangle contains no points other than its vertices.

Original entry on oeis.org

3, 10, 33, 96, 235, 486, 933, 1600, 2561, 3884, 5907, 8310, 11793, 15890, 20863, 27002, 35229, 44117, 55820, 68312, 82931, 100368, 121711, 143685, 169750, 199509, 232366, 268169, 312132, 355839, 409902, 465503, 527080, 596443, 668961, 746443, 839830, 937967

Offset: 1

Scott R. Shannon and N. J. A. Sloane, Mar 05 2020

nonn

See the links in A332953 for images of the triangles.

Lars Blomberg, Table of n, a(n) for n = 1..70

Cf. A332953 (regions), A333025 (n-gons), A333026 (vertices), A007678, A092867, A331452, A331911, A332357, A332358.

a(16) and beyond from Lars Blomberg, May 26 2020

A333026 The number of vertices formed on an isosceles triangle by straight line segments mutually connecting all vertices and all points that divide the two equal length sides into n equal parts; the base of the triangle contains no points other than its vertices.

Original entry on oeis.org

3, 6, 16, 45, 111, 230, 448, 769, 1229, 1858, 2860, 4007, 5737, 7724, 10115, 13074, 17172, 21454, 27288, 33332, 40413, 48944, 59594, 70213, 82983, 97608, 113672, 131032, 152986, 174088, 201090, 228295, 258467, 292726, 328080, 365633, 412291, 460834, 512016

Offset: 1

Scott R. Shannon and N. J. A. Sloane, Mar 05 2020

nonn

See the links in A332953 for images of the triangles.

Lars Blomberg, Table of n, a(n) for n = 1..70

Cf. A332953 (regions), A333025 (n-gons), A333027 (edges), A007678, A092867, A331452, A331911, A332357, A332358.

a(16) and beyond from Lars Blomberg, May 26 2020

A333037 Table read by rows: T(n,k) = number of k-sided polygons in an equal-armed cross with arms of length n (see Comments in A331456 for definition) for k = 3,4,5,6,7.

Original entry on oeis.org

4, 0, 0, 0, 0, 84, 20, 0, 0, 0, 380, 180, 0, 8, 0, 1076, 764, 40, 20, 0, 2380, 2316, 64, 48, 0, 4716, 5188, 224, 52, 0, 8236, 10492, 360, 92, 0, 13620, 18772, 632, 108, 0, 21188, 31380, 864, 196, 0, 31596, 49228, 1376, 224, 8, 44980, 74268, 1920, 272, 8

Offset: 0

Scott R. Shannon and N. J. A. Sloane, Mar 06 2020

See the links in A331456 for images of the crosses.

			Table begins:
4, 0, 0, 0, 0
84, 20, 0, 0, 0
380, 180, 0, 8, 0
1076, 764, 40, 20, 0
2380, 2316, 64, 48, 0
4716, 5188, 224, 52, 0
8236, 10492, 360, 92, 0
13620, 18772, 632, 108, 0
21188, 31380, 864, 196, 0
31596, 49228, 1376, 224, 8
44980, 74268, 1920, 272, 8
The row sums are A331456.

Cf. A331456 (regions), A333035 (vertices), A333036 (edges), A331451, A332723, A333025.

A333458 Irregular table read by rows: Take a diagonal-edged (or diamond-shaped) checkerboard with all diagonals drawn, as in A333434. Then T(n,k) = number of k-sided polygons in that figure for k >= 3.

Original entry on oeis.org

4, 84, 20, 692, 312, 72, 4, 2708, 2020, 400, 88, 0, 4, 7876, 5764, 1580, 264, 20, 4, 18220, 14868, 4960, 904, 112, 24, 36764, 30624, 11224, 2496, 304, 52, 66004, 55192, 18624, 3952, 472, 48, 111764, 97840, 40008, 9912, 1740, 244, 36, 175156, 158280, 63632, 15744, 2560, 156, 8, 16

Offset: 1

Scott R. Shannon and N. J. A. Sloane, Mar 22 2020

See A333434 for the definition and images of the checkerboard.

			Table begins:
4;
84, 20;
692, 312, 72, 4;
2708, 2020, 400, 88, 0, 4;
7876, 5764, 1580, 264, 20, 4;
18220, 14868, 4960, 904, 112, 24;
36764, 30624, 11224, 2496, 304, 52;
66004, 55192, 18624, 3952, 472, 48;
111764, 97840, 40008, 9912, 1740, 244, 36;
175156, 158280, 63632, 15744, 2560, 156, 8, 16;
...

Lars Blomberg, Table of n, a(n) for n = 1..201 (the first 27 rows)

Cf. A333434 (regions), A333459 (vertices), A333460 (edges), A331911, A331451, A333025, A333037.

a(32) and beyond from Lars Blomberg, Jun 03 2020

A330914 Irregular table read by rows: Take a semicircular polygon with all vertices mutually connected by straight line segments, as in A333642. Then T(n,k) = number of k-sided polygons in that figure for k >= 3.

Original entry on oeis.org

2, 7, 1, 16, 4, 30, 10, 3, 52, 20, 8, 79, 47, 10, 3, 116, 86, 18, 4, 168, 145, 9, 2, 234, 212, 52, 12, 319, 312, 80, 17, 2, 430, 446, 96, 18, 2, 551, 616, 173, 28, 5, 730, 792, 248, 44, 6, 960, 1035, 167, 25, 1148, 1384, 422, 66, 20

Offset: 1

Scott R. Shannon and N. J. A. Sloane, May 02 2020

See A333642 for a precise definition of the polygon and images.

			Table begins:
2;
7,1;
16,4;
30,10,3;
52,20,8;
79,47,10,3;
116,86,18,4;
168,145,9,2;
234,212,52,12;
319,312,80,17,2;
430,446,96,18,2;
551,616,173,28,5;
730,792,248,44,6;
960,1035,167,25;
1148,1384,422,66,20;
1427,1745,552,108,12;
1784,2154,648,120,14;
2179,2618,927,164,27,1
2652,3200,1088,244,36;
3237,3842,1170,218,26,3,2;

Cf. A333642 (regions), A330911 (edges), A330913 (vertices), A331932, A333025, A331451.

cp's OEIS Frontend

A332953 The number of regions formed inside an isosceles triangle by straight line segments mutually connecting all vertices and all points that divide the two equal length sides into n equal parts; the base of the triangle contains no points other than its vertices.

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A333027 The number of edges formed on an isosceles triangle by straight line segments mutually connecting all vertices and all points that divide the two equal length sides into n equal parts; the base of the triangle contains no points other than its vertices.

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A333026 The number of vertices formed on an isosceles triangle by straight line segments mutually connecting all vertices and all points that divide the two equal length sides into n equal parts; the base of the triangle contains no points other than its vertices.

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A333037 Table read by rows: T(n,k) = number of k-sided polygons in an equal-armed cross with arms of length n (see Comments in A331456 for definition) for k = 3,4,5,6,7.

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A333458 Irregular table read by rows: Take a diagonal-edged (or diamond-shaped) checkerboard with all diagonals drawn, as in A333434. Then T(n,k) = number of k-sided polygons in that figure for k >= 3.

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Examples

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Crossrefs

Extensions

A330914 Irregular table read by rows: Take a semicircular polygon with all vertices mutually connected by straight line segments, as in A333642. Then T(n,k) = number of k-sided polygons in that figure for k >= 3.

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