A177719 -id:A177719 - cp's OEIS frontend

A324043 Number of quadrilateral regions into which a figure made up of a row of n adjacent congruent rectangles is divided upon drawing diagonals of all possible rectangles.

0, 2, 14, 34, 90, 154, 288, 462, 742, 1038, 1512, 2074, 2904, 3774, 4892, 6154, 7864, 9662, 12022, 14638, 17786, 20998, 25024, 29402, 34672, 40038, 46310, 53038, 61090, 69454, 79344, 89890, 101792, 113854, 127476, 141866, 158428, 175182, 193760, 213274, 235444, 258182, 283858, 310750, 339986

Offset: 1

Jinyuan Wang, May 01 2019

nonn

A row of n adjacent congruent rectangles can only be divided into triangles (cf. A324042) or quadrilaterals when drawing diagonals. Proof is given in Alekseyev et al. (2015) under the transformation described in A306302.

			For k adjacent congruent rectangles, the number of quadrilateral regions in the j-th rectangle is:
k\j|  1   2   3   4   5   6   7  ...
---+--------------------------------
1  |  0,  0,  0,  0,  0,  0,  0, ...
2  |  1,  1,  0,  0,  0,  0,  0, ...
3  |  3,  8,  3,  0,  0,  0,  0, ...
4  |  5, 12, 12,  5,  0,  0,  0, ...
5  |  7, 22, 32, 22,  7,  0,  0, ...
6  |  9, 28, 40, 40, 28,  9,  0, ...
7  | 11, 38, 58, 74, 58, 38, 11, ...
...
a(4) = 5 + 12 + 12 + 5 = 34.

Chai Wah Wu, Table of n, a(n) for n = 1..10000
M. A. Alekseyev, M. Basova, and N. Yu. Zolotykh, On the minimal teaching sets of two-dimensional threshold functions. SIAM Journal on Discrete Mathematics 29:1 (2015), 157-165.
Lars Blomberg, Scott R. Shannon, and N. J. A. Sloane, Graphical Enumeration and Stained Glass Windows, 1: Rectangular Grids, (2021). Also arXiv:2009.07918.
Robert Israel, Maple program.
Jinyuan Wang, Illustration for n = 1, 2, 3, 4, 5.

Cf. A007678, A108914, A114043, A115005, A177719, A306302, A324042, A333286, A333287, A333288.

See Robert Israel link.
There are also Maple programs for both A306302 and A324042. Then a := n -> A306302(n) - A324042(n); # N. J. A. Sloane, Mar 04 2020

Table[Sum[Sum[(Boole[GCD[i, j] == 1] - 2 * Boole[GCD[i, j] == 2]) * (n + 1 - i) * (n + 1 - j), {j, 1, n}], {i, 1, n}] - n^2, {n, 1, 45}] (* Joshua Oliver, Feb 05 2020 *)

{ A324043(n) = sum(i=1, n, sum(j=1, n, ( (gcd(i, j)==1) - 2*(gcd(i,j)==2) ) * (n+1-i) * (n+1-j) )) - n^2; } \\ Max Alekseyev, Jul 08 2019

from sympy import totient
def A324043(n): return 0 if n==1 else -2*(n-1)**2 + sum(totient(i)*(n+1-i)*(7*i-2*n-2) for i in range(2,n//2+1)) + sum(totient(i)*(n+1-i)*(2*n+2-i) for i in range(n//2+1,n+1)) # Chai Wah Wu, Aug 16 2021

a(n) = A115005(n+1) - A177719(n+1) - n - 1 = Sum_{i,j=1..n; gcd(i,j)=1} (n+1-i)*(n+1-j) - 2*Sum_{i,j=1..n; gcd(i,j)=2} (n+1-i)*(n+1-j) - n^2. - Max Alekseyev, Jul 08 2019
a(n) = A306302(n) - A324042(n).
For n>1, a(n) = -2(n-1)^2 + Sum_{i=2..floor(n/2)} (n+1-i)*(7i-2n-2)*phi(i) + Sum_{i=floor(n/2)+1..n} (n+1-i)*(2n+2-i)*phi(i). - Chai Wah Wu, Aug 16 2021

a(8)-a(23) from Robert Israel, Jul 07 2019

Terms a(24) onward from Max Alekseyev, Jul 08 2019

A324042 Number of triangular regions into which a figure made up of a row of n adjacent congruent rectangles is divided upon drawing diagonals of all possible rectangles.

Original entry on oeis.org

4, 14, 32, 70, 124, 226, 360, 566, 820, 1218, 1696, 2310, 3020, 4018, 5160, 6590, 8196, 10218, 12464, 15110, 18012, 21650, 25624, 30142, 35028, 40954, 47344, 54558, 62284, 71034, 80360, 90806, 101892, 114770, 128416, 143286, 158972, 176914, 195816, 216350, 237908, 261546, 286304, 313102, 341100

Offset: 1

Jinyuan Wang, May 01 2019

nonn

A row of n adjacent congruent rectangles can only be divided into triangles or quadrilaterals when drawing diagonals. A proof is given in Alekseyev et al. (2015) using the mapping to a dissection of a a right isosceles triangle described in A306302.

			For k adjacent congruent rectangles, the number of triangular regions in the j-th rectangle is:
k\j|  1   2   3   4   5   6   7  ...
---+--------------------------------
1  |  4,  0,  0,  0,  0,  0,  0, ...
2  |  7,  7,  0,  0,  0,  0,  0, ...
3  |  9, 14,  9,  0,  0,  0,  0, ...
4  | 11, 24, 24, 11,  0,  0,  0, ...
5  | 13, 30, 38, 30, 13,  0,  0, ...
6  | 15, 38, 60, 60, 38, 15,  0, ...
7  | 17, 44, 76, 86, 76, 44, 17, ...
...
a(4) = 11 + 24 + 24 + 11 = 70.

Chai Wah Wu, Table of n, a(n) for n = 1..10000
M. A. Alekseyev, M. Basova, and N. Yu. Zolotykh. On the minimal teaching sets of two-dimensional threshold functions. SIAM Journal on Discrete Mathematics 29:1 (2015), 157-165.
Lars Blomberg, Scott R. Shannon, and N. J. A. Sloane, Graphical Enumeration and Stained Glass Windows, 1: Rectangular Grids, (2021). Also arXiv:2009.07918.
Robert Israel, Maple program
Jinyuan Wang, Illustration for n = 1, 2, 3, 4, 5

Cf. A177719, A306302, A324043, A333286, A333287, A333288.

V := proc(m,n,q) local a,i,j; a:=0;
for i from 1 to m do for j from 1 to n do
if gcd(i,j)=q then a:=a+(m+1-i)*(n+1-j); fi; od: od: a; end;
a := n -> 2*( n*(n+1) + V(n,n,2) );
[seq(a(n), n=1..30)]; # N. J. A. Sloane, Mar 04 2020
See also Robert Israel link.

Table[2 * (n^2 + n + Sum[Sum[Boole[GCD[i, j] == 2] * (n + 1 - i) * (n + 1 - j), {j, 1, n}], {i, 1, n}]), {n, 1, 45}]  (* Joshua Oliver, Feb 05 2020 *)

{ A324042(n) = 2*((n+1)*n + sum(i=1, n, sum(j=1, n, (gcd(i, j)==2)*(n+1-i)*(n+1-j))) ); } \\ Max Alekseyev, Jul 08 2019

from sympy import totient
def A324042(n): return 2*(2*n**2-n+1 + 2*sum(totient(i)*(n+1-2*i)*(n+1-i) for i in range(2,n//2+1))) # Chai Wah Wu, Aug 16 2021

a(n) = A177719(n+1) + 2*(n+1) = 2 * ( (n+1)*n + Sum_{i,j=1..n; gcd(i,j)=2} (n+1-i)*(n+1-j) ). - Max Alekseyev, Jul 08 2019
a(n) = A306302(n) - A324043(n).
a(n) = 2*(2*n^2-n+1+2*Sum_{i=2..floor(n/2)} (n+1-2*i)*(n+1-i)*phi(i)). - Chai Wah Wu, Aug 16 2021

a(8)-a(23) from Robert Israel, Jul 07 2019

Terms a(24) onward from Max Alekseyev, Jul 08 2019

A332353 Triangle read by rows: T(m,n) = Sum_{-m= n >= 1.

Original entry on oeis.org

0, 0, 0, 1, 2, 8, 2, 4, 14, 24, 3, 6, 22, 38, 60, 4, 8, 30, 52, 82, 112, 5, 10, 40, 70, 112, 154, 212, 6, 12, 50, 88, 142, 196, 270, 344, 7, 14, 62, 110, 178, 246, 340, 434, 548, 8, 16, 74, 132, 214, 296, 410, 524, 662, 800, 9, 18, 88, 158, 258, 358, 498, 638, 808, 978, 1196

Offset: 1

N. J. A. Sloane, Feb 10 2020

This is the triangle in A332352, halved.

			Triangle begins:
0,
0, 0,
1, 2, 8,
2, 4, 14, 24,
3, 6, 22, 38, 60,
4, 8, 30, 52, 82, 112,
5, 10, 40, 70, 112, 154, 212,
6, 12, 50, 88, 142, 196, 270, 344,
7, 14, 62, 110, 178, 246, 340, 434, 548,
8, 16, 74, 132, 214, 296, 410, 524, 662, 800,
...

Paolo Xausa, Table of n, a(n) for n = 1..11325 (rows 1..150 of the triangle, flattened)
M. A. Alekseyev, M. Basova, and N. Yu. Zolotykh. On the minimal teaching sets of two-dimensional threshold functions. SIAM Journal on Discrete Mathematics 29:1 (2015), 157-165. doi:10.1137/140978090. This sequence is f_2(m,n)/2.

The main diagonal is A177719.

Cf. A332350, A332352.

VR := proc(m,n,q) local a,i,j; a:=0;
for i from -m+1 to m-1 do for j from -n+1 to n-1 do
if gcd(i,j)=q then a:=a+(m-abs(i))*(n-abs(j)); fi; od: od: a; end;
for m from 1 to 12 do lprint(seq(VR(m,n,2)/2,n=1..m),); od:

A332353[m_,n_]:=Sum[If[GCD[i,j]==2,2(m-i)(n-j),0],{i,2,m-1,2},{j,2,n-1,2}]+If[n>2,m*n-2m,0]+If[m>2,m*n-2n,0];Table[A332353[m, n],{m,15},{n, m}] (* Paolo Xausa, Oct 18 2023 *)

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A324043 Number of quadrilateral regions into which a figure made up of a row of n adjacent congruent rectangles is divided upon drawing diagonals of all possible rectangles.

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A324042 Number of triangular regions into which a figure made up of a row of n adjacent congruent rectangles is divided upon drawing diagonals of all possible rectangles.

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Author

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Examples

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Crossrefs

Programs

Maple

Mathematica

PARI

Python

Formula

Extensions

A332353 Triangle read by rows: T(m,n) = Sum_{-m= n >= 1.

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Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Maple

Mathematica