a(n) is the number of 4 element sets of distinct integer sided trapezoids whose base angles are 60 degrees that fill an equilateral triangular grid of side n units.

A389392

a(n) is the number of 4 element sets of distinct integer sided trapezoids whose base angles are 60 degrees that fill an equilateral triangular grid of side n units.

Terms

    a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =9a(6) =20a(7) =40a(8) =66a(9) =101a(10) =149a(11) =207a(12) =280a(13) =365a(14) =468a(15) =589a(16) =729a(17) =882a(18) =1068a(19) =1269a(20) =1494a(21) =1746a(22) =2029a(23) =2328a(24) =2672a(25) =3034a(26) =3432a(27) =3866a(28) =4337a(29) =4827

External references