Number of ways to place 3 points on a triangular grid of side n so that they are not vertices of an equilateral triangle of any orientation.

A240440

Number of ways to place 3 points on a triangular grid of side n so that they are not vertices of an equilateral triangle of any orientation.

Terms

    a(0) =0a(1) =0a(2) =15a(3) =105a(4) =420a(5) =1260a(6) =3150a(7) =6930a(8) =13860a(9) =25740a(10) =45045a(11) =75075a(12) =120120a(13) =185640a(14) =278460a(15) =406980a(16) =581400a(17) =813960a(18) =1119195a(19) =1514205a(20) =2018940a(21) =2656500a(22) =3453450a(23) =4440150a(24) =5651100a(25) =7125300a(26) =8906625a(27) =11044215a(28) =13592880a(29) =16613520

External references