Number of collinear triples in a 4 X n rectangular grid.

Terms

a(0) =4a(1) =8a(2) =20a(3) =44a(4) =84a(5) =140a(6) =224a(7) =332a(8) =472a(9) =648a(10) =864a(11) =1120a(12) =1428a(13) =1784a(14) =2196a(15) =2668a(16) =3204a(17) =3804a(18) =4480a(19) =5228a(20) =6056a(21) =6968a(22) =7968a(23) =9056a(24) =10244a(25) =11528a(26) =12916a(27) =14412a(28) =16020a(29) =17740