Number of ways to choose four collinear points from an n X n grid.

Terms

a(0) =0a(1) =0a(2) =0a(3) =10a(4) =64a(5) =234a(6) =660a(7) =1524a(8) =3156a(9) =5928a(10) =10428a(11) =17154a(12) =27340a(13) =41506a(14) =61176a(15) =87756a(16) =123216a(17) =168420a(18) =227208a(19) =300054a(20) =391920a(21) =504886a(22) =642604a(23) =806424a(24) =1006404a(25) =1242024a(26) =1519980a(27) =1845150a(28) =2226804a(29) =2663574