A092275 Draw a line through every pair of points with coordinates (x, 1) and (x', 2) with x, x' in 1..n, and then count the number of intersection points above the line y = 2.

0, 2, 11, 29, 69, 125, 224, 361, 563, 809, 1164, 1597, 2188, 2871, 3714, 4701, 5956, 7359, 9099, 11067, 13365, 15879, 18884, 22201, 26056, 30219, 34951, 40117, 46073, 52441, 59716, 67599, 76320, 85569, 95790, 106701, 118902

Offset

2,2

Links

Table of n, a(n) for n=2..38.

Joseph O'Rourke, Art Gallery Theorems and Algorithms, Oxford Univ. Press, 1987. See section 8.6, p. 223.

Formula

a(n) = (A347750(n+1) - A331755(n)) / 2. - Andrey Zabolotskiy, Jan 17 2024

Crossrefs

Cf. A331755, A347750.

Sequence in context: A024178 A009312 A154251 * A295841 A086252 A106926

Adjacent sequences: A092272 A092273 A092274 * A092276 A092277 A092278

Keyword

nonn

Author

N. J. A. Sloane, Feb 17 2004

Extensions

New name and terms a(10) and beyond (using the formula) added by Andrey Zabolotskiy, Jan 18 2024

Status

approved