Number of line segments connecting exactly 7 points in an n X n grid of points.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =16a(7) =40a(8) =72a(9) =112a(10) =160a(11) =216a(12) =308a(13) =416a(14) =540a(15) =680a(16) =836a(17) =1008a(18) =1276a(19) =1576a(20) =1908a(21) =2272a(22) =2668a(23) =3096a(24) =3660a(25) =4272a(26) =4932a(27) =5640a(28) =6396a(29) =7200