Number of collinear point 7-tuples in an n X n cubical grid.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =16a(7) =148a(8) =756a(9) =2820a(10) =8580a(11) =22572a(12) =53224a(13) =115036a(14) =231960a(15) =441032a(16) =799064a(17) =1387368a(18) =2324744a(19) =3771176a(20) =5952528a(21) =9159392a(22) =13791008a(23) =20340036a(24) =29476508a(25) =41992820a(26) =58953420a(27) =81591788a(28) =111535064a(29) =150611100