One-half of the number of lines through at least 2 points of an n X n grid of points.

Terms

a(0) =0a(1) =0a(2) =3a(3) =10a(4) =31a(5) =70a(6) =153a(7) =268a(8) =469a(9) =746a(10) =1153a(11) =1648a(12) =2361a(13) =3230a(14) =4415a(15) =5784a(16) =7473a(17) =9450a(18) =11963a(19) =14772a(20) =18255a(21) =22194a(22) =26793a(23) =31824a(24) =37837a(25) =44474a(26) =52187a(27) =60516a(28) =69983a(29) =80318