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.
%I A175383 #36 Feb 16 2025 08:33:12 %S A175383 0,1,78,1278,9498,47331,175952,545764,1461672,3507553,7701638, %T A175383 15773526,30375194,55695587,97777392,165310348,270478344,430196181, %U A175383 666685134,1010083690,1498720098,2182544223 %N A175383 Number of complete quadrangles on an n X n grid (or geoplane). %C A175383 A complete quadrangle is a set of four points, no three collinear, and the six lines which join them. %C A175383 Number of ways to arrange 4 indistinguishable points on an n X n square grid so that no three points are collinear at any angle. Column 4 of A194193. - _R. H. Hardin_, Aug 18 2011 %H A175383 R. H. Hardin, <a href="/A175383/b175383.txt">Table of n, a(n) for n = 1..55</a> %H A175383 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CompleteQuadrangle.html">Complete Quadrangle</a>. %F A175383 a(n) = A189345(n) - A189346(n) - A178256(n). %F A175383 a(n) = (1/3)*A189412(n) + A189413(n). %e A175383 From _R. H. Hardin_, Aug 18 2011: (Start) %e A175383 Some solutions for 3 X 3: %e A175383 0 1 1 1 1 0 1 0 1 0 1 1 0 0 0 1 1 0 1 1 0 %e A175383 1 0 0 0 0 0 1 0 0 1 1 0 1 1 0 0 0 1 1 0 0 %e A175383 1 0 0 1 0 1 0 0 1 0 0 0 0 1 1 0 1 0 0 1 0 %e A175383 (End) %K A175383 nonn %O A175383 1,3 %A A175383 _Martin Renner_, Apr 19 2011 %E A175383 a(6)-a(22) from _Nathaniel Johnston_, Apr 25 2011 %E A175383 a(7)-a(22) corrected by _Nathaniel Johnston_, based on another correction by Michal ForiĊĦek, Sep 06 2011