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 A178256 #20 Jun 15 2020 21:39:18 %S A178256 0,0,0,10,64,234,660,1524,3156,5928,10428,17154,27340,41506,61176, %T A178256 87756,123216,168420,227208,300054,391920,504886,642604,806424, %U A178256 1006404,1242024,1519980,1845150,2226804,2663574,3175048,3754936,4420440,5175840,6030840 %N A178256 Number of ways to choose four collinear points from an n X n grid. %H A178256 Tomas Rokicki and Tom Duff, <a href="/A178256/b178256.txt">Table of n, a(n) for n = 1..1000</a> (First 48 terms from R. H. Hardin.) %e A178256 a(1) = a(2) = a(3) = 0 since there are no collinear point quadruples %e A178256 a(4) = 4 rows + 4 columns + 2 diagonals = 10 %e A178256 a(5) = binomial(5,4)*(5 rows + 5 columns + 2 diagonals) + 4 secondary diagonals = 64 %e A178256 a(6) = binomial(6,4)*(6 rows + 6 columns + 2 diagonals) + binomial(5,4)*(4 secondary diagonals) + 4 third diagonals = 234 %Y A178256 Cf. A000938, A157882. %Y A178256 This is the main diagonal of A334708. %K A178256 nonn %O A178256 1,4 %A A178256 _R. H. Hardin_, suggested by R. J. Mathar in the Sequence Fans Mailing List, May 24 2010