A288180 - OEIS

A288180

Number of intersection points formed by drawing the line segments connecting any two lattice points of an n X m convex lattice polygon written as triangle T(n,m), n >= 1, 1 <= m <= n.

5, 13, 37, 35, 121, 353, 75, 265, 771, 1761, 159, 587, 1755, 4039, 8917, 275, 1019, 3075, 7035, 15419, 26773, 477, 1797, 5469, 12495, 27229, 47685, 84497, 755, 2823, 8693, 19831, 43333, 76357, 135075, 215545, 1163, 4369, 13301, 30333, 66699, 117719, 207643, 331233, 508613

(list; table; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

If more than two lines intersect in the same point, only one intersection is counted.

REFERENCES

For references and links see A288177.

LINKS

Lars Blomberg, Table of n, a(n) for n = 1..325 (The first 25 rows)

Lars Blomberg, Scott R. Shannon, N. J. A. Sloane, Graphical Enumeration and Stained Glass Windows, 1: Rectangular Grids, (2021). Also arXiv:2009.07918.

Hugo Pfoertner, Illustrations of Chamber Complexes up to 5 X 5.

Hugo Pfoertner, Illustration of intersection points up to 6 X 6.