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 1-7 of 7 results.

A359690 Number of vertices in a regular drawing of a complete bipartite graph where the vertex positions on each part equal the Farey series of order n.

Original entry on oeis.org

5, 13, 69, 289, 1971, 3997, 20371, 45751, 120957, 205299, 629847, 897801, 2334409, 3461459, 5517131, 8468061
Offset: 1

Views

Author

Scott R. Shannon and N. J. A. Sloane, Jan 11 2023

Keywords

Comments

The number of vertices along each edge is A005728(n). No formula for a(n) is known.

Links

Crossrefs

Cf. A359691 (crossings), A359692 (regions), A359693 (edges), A359694 (k-gons), A005728, A331755, A359654, A358887, A358883, A006842, A006843.

Formula

a(n) = A359693(n) - A359692(n) + 1 by Euler's formula.

A359693 Number of edges in a regular drawing of a complete bipartite graph where the vertex positions on each part equal the Farey series of order n.

Original entry on oeis.org

6, 24, 162, 670, 4456, 8942, 44470, 98902, 259114, 438552, 1330566, 1897164, 4893752, 7246502, 11544278, 17678880
Offset: 1

Views

Author

Scott R. Shannon and N. J. A. Sloane, Jan 11 2023

Keywords

Comments

The number of vertices along each edge is A005728(n). No formula for a(n) is known.
See A359690 and A359692 for images of the graph.

Links

Crossrefs

Cf. A359690 (vertices), A359691 (crossings), A359692 (regions), A359694 (k-gons), A005728, A290132, A359655, A358888, A358884, A006842, A006843.

Formula

a(n) = A359690(n) + A359692(n) - 2*A005728(n) + 1 by Euler's formula.

A359692 Number of regions in a regular drawing of a complete bipartite graph where the vertex positions on each part equal the Farey series of order n.

Original entry on oeis.org

2, 12, 94, 382, 2486, 4946, 24100, 53152, 138158, 233254, 700720, 999364, 2559344, 3785044, 6027148, 9210820
Offset: 1

Views

Author

Scott R. Shannon and N. J. A. Sloane, Jan 11 2023

Keywords

Comments

The number of vertices along each edge is A005728(n). No formula for a(n) is known.

Links

Crossrefs

Cf. A359690 (vertices), A359691 (crossings), A359693 (edges), A359694 (k-gons), A005728, A290131, A359653, A358886, A358882, A006842, A006843.

Formula

a(n) = A359693(n) - A359690(n) + 1 by Euler's formula.

A359971 Irregular table read by rows: T(n,k) is the number of k-gons, k>=3, formed inside a right triangle by the straight line segments mutually connecting all vertices and points on the two shorter edges whose positions equal the Farey series of order n.

Original entry on oeis.org

1, 5, 33, 15, 108, 126, 5, 727, 1031, 38, 2, 1314, 2452, 167, 15, 2, 6811, 12102, 988, 52, 14904, 27626, 3255, 214, 4, 2, 2, 39172, 73289, 10062, 795, 19, 1, 65833, 127951, 18476, 1464, 64, 5, 201643, 370880, 59630, 5548, 250, 7, 2, 288196, 541258, 91037, 9692, 428, 20, 4, 741597, 1351301, 239180, 27510, 1434, 58
Offset: 1

Views

Author

Scott R. Shannon and N. J. A. Sloane, Jan 20 2023

Keywords

Comments

The number of vertices along the shorter edges is A005728(n).
No formula for a(n) is known. The sequence is inspired by the Farey fan; see A360042.
See A359968 and A359969 for images of the triangle.

Examples

			The table begins:
        1;
        5;
       33,      15;
      108,     126,      5;
      727,    1031,     38,     2;
     1314,    2452,    167,    15,    2;
     6811,   12102,    988,    52;
    14904,   27626,   3255,   214,    4,   2, 2;
    39172,   73289,  10062,   795,   19,   1;
    65833,  127951,  18476,  1464,   64,   5;
   201643,  370880,  59630,  5548,  250,   7, 2;
   288196,  541258,  91037,  9692,  428,  20, 4;
   741597, 1351301, 239180, 27510, 1434,  58;
  1095197, 2025237, 374907, 44880, 2491, 104, 4, 2;
  1747260, 3279178, 628335, 76787, 4600, 178, 6;
  ...

Crossrefs

Cf. A359968 (vertices), A359969 (regions and row sums), A359970 (edges), A005728, A360042, A359977, A359694, A358951, A358889.

A359977 Irregular table read by rows: T(n,k) is the number of k-gons, k>=3, formed inside a right triangle by the straight line segments mutually connecting all vertices and points on the two shorter edges whose positions on one edge equal the Farey series of order n while on the other they divide its length into n equal segments.

Original entry on oeis.org

1, 5, 20, 8, 2, 50, 57, 3, 169, 274, 31, 5, 303, 646, 41, 2, 1, 889, 2011, 179, 21, 2, 1685, 4025, 388, 33, 4, 3466, 8283, 925, 67, 7, 5624, 13442, 1498, 106, 9, 1, 11896, 27907, 3718, 354, 30, 2, 16976, 40100, 5182, 461, 33, 1, 32506, 73806, 11249, 1118, 61, 6, 46187, 104453, 16380, 1747, 123, 1, 1
Offset: 1

Views

Author

Scott R. Shannon and N. J. A. Sloane, Jan 20 2023

Keywords

Comments

The number of vertices on the edge with point positions equaling the Farey series of order n is A005728(n). No formula for a(n) is known.
See A359974 and A359975 for images of the triangle.
This graph is related to the 'Farey fan' given in the reference.

Examples

			The table begins:
1;
5;
20, 8, 2;
50, 57, 3;
169, 274, 31, 5;
303, 646, 41, 2, 1;
889, 2011, 179, 21, 2;
1685, 4025, 388, 33, 4;
3466, 8283, 925, 67, 7;
5624, 13442, 1498, 106, 9, 1;
11896, 27907, 3718, 354, 30, 2;
16976, 40100, 5182, 461, 33, 1;
32506, 73806, 11249, 1118, 61, 6;
46187, 104453, 16380, 1747, 123, 1, 1;
67117, 152534, 24159, 2511, 181, 10, 1;
95276, 213798, 34962, 3824, 295, 21;
.
.

References

  • McIlroy, M. D. "A Note on Discrete Representation of Lines". AT&T Technical Journal, 64 (1985), 481-490.

Crossrefs

Cf. A359974 (vertices), A359975 (regions), A359976 (edges), A005728, A359971, A359694, A358951, A358889.

Formula

Sum of row n = A359975(n).

A359691 Number of crossings in a regular drawing of a complete bipartite graph where the vertex positions on each part equal the Farey series of order n.

Original entry on oeis.org

1, 7, 59, 275, 1949, 3971, 20333, 45705, 120899, 205233, 629761, 897707, 2334291, 3461329, 5516985, 8467899
Offset: 1

Views

Author

Scott R. Shannon and N. J. A. Sloane, Jan 11 2023

Keywords

Comments

The number of vertices along each edge is A005728(n). No formula for a(n) is known.
See A359690 for images of the graph.

Links

Crossrefs

Cf. A359690 (vertices), A359692 (regions), A359693 (edges), A359694 (k-gons), A005728, A159065, A331755, A359654, A358887, A358883, A006842, A006843.

Formula

a(n) = A359690(n) - 2*A005728(n).

A360044 Table read by rows: T(n,k) is the number of k-gons, 3<=k<=4, in a Farey fan of order n.

Original entry on oeis.org

0, 1, 4, 0, 6, 2, 10, 4, 14, 10, 22, 14, 30, 24, 42, 34, 54, 50, 74, 62, 94, 84, 118, 106, 142, 140, 178, 168, 214, 204, 258, 240, 302, 292, 358, 338, 414, 402, 478, 466, 542, 542, 626, 608, 710, 696, 802, 784, 894, 892, 1010, 988, 1126, 1102, 1254, 1216, 1382, 1358, 1526, 1492
Offset: 1

Views

Author

Scott R. Shannon, N. J. A. Sloane and M. Douglas McIlroy , Jan 23 2023

Keywords

Comments

See the reference for the definition of a 'Farey fan', along with a proof that only 3-gons and 4-gons are created. See A360042 for further details and images of the graph.

Examples

			The table begins:
0, 1;
4, 0;
6, 2;
10, 4;
14, 10;
22, 14;
30, 24;
42, 34;
54, 50;
74, 62;
94, 84;
118, 106;
142, 140;
178, 168;
214, 204;
.
.

Links

Crossrefs

Cf. A005598 (regions), A360042 (vertices), A360043 (edges), A005728, A174030, A359977, A359971, A359694.
Showing 1-7 of 7 results.

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

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