Number of collinear point triples on a centered hexagonal grid of size n.

Terms

a(0) =0a(1) =3a(2) =69a(3) =390a(4) =1314a(5) =3441a(6) =7503a(7) =14388a(8) =25692a(9) =42471a(10) =66417a(11) =100194a(12) =145206a(13) =204429a(14) =280971a(15) =377400a(16) =496608a(17) =642891a(18) =821925a(19) =1034742a(20) =1288602a(21) =1587009a(22) =1933695a(23) =2339100a(24) =2802804a(25) =3334983a(26) =3942585a(27) =4627002a(28) =5404542a(29) =6278661