Number of lines through exactly 2 points of an n X n grid of points.

Terms

a(0) =0a(1) =0a(2) =6a(3) =12a(4) =48a(5) =108a(6) =248a(7) =428a(8) =764a(9) =1196a(10) =1900a(11) =2668a(12) =3824a(13) =5244a(14) =7248a(15) =9380a(16) =12192a(17) =15372a(18) =19528a(19) =24020a(20) =29732a(21) =36052a(22) =43808a(23) =51836a(24) =61636a(25) =72492a(26) =85308a(27) =98492a(28) =114012a(29) =130668