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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.

%I A092275 #13 Jun 19 2025 16:15:50
%S A092275 0,2,11,29,69,125,224,361,563,809,1164,1597,2188,2871,3714,4701,5956,
%T A092275 7359,9099,11067,13365,15879,18884,22201,26056,30219,34951,40117,
%U A092275 46073,52441,59716,67599,76320,85569,95790,106701,118902
%N 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.
%H A092275 Joseph O'Rourke, <a href="https://www.science.smith.edu/~jorourke/books/ArtGalleryTheorems/art.html">Art Gallery Theorems and Algorithms</a>, Oxford Univ. Press, 1987. See section 8.6, p. 223.
%F A092275 a(n) = (A347750(n-1) - A331755(n)) / 2. - _Andrey Zabolotskiy_, Jan 17 2024
%Y A092275 Cf. A331755, A347750.
%K A092275 nonn
%O A092275 2,2
%A A092275 _N. J. A. Sloane_, Feb 17 2004
%E A092275 New name and terms a(10) and beyond (using the formula) added by _Andrey Zabolotskiy_, Jan 18 2024