Number of ways to choose three points on a centered hexagonal grid of size n.

Terms

a(0) =0a(1) =35a(2) =969a(3) =7770a(4) =35990a(5) =121485a(6) =333375a(7) =790244a(8) =1679580a(9) =3280455a(10) =5989445a(11) =10349790a(12) =17083794a(13) =27128465a(14) =41674395a(15) =62207880a(16) =90556280a(17) =128936619a(18) =180007425a(19) =246923810a(20) =333395790a(21) =443749845a(22) =582993719a(23) =756884460a(24) =971999700a(25) =1235812175a(26) =1556767485a(27) =1944365094