Number of non-equivalent ways to choose 5 points in an equilateral triangle grid of side n.

Terms

a(0) =0a(1) =0a(2) =2a(3) =48a(4) =526a(5) =3450a(6) =16536a(7) =63104a(8) =204202a(9) =580669a(10) =1491096a(11) =3520768a(12) =7754502a(13) =16098425a(14) =31770760a(15) =59998736a(16) =109022244a(17) =191454654a(18) =326158974a(19) =540703008a(20) =874630262a(21) =1383621756a(22) =2144889472a(23) =3263884272a(24) =4882793214a(25) =7190910467a(26) =10437526372a(27) =14947411024