Theta series of hexagonal close-packing with respect to triangle between octahedra.

Terms

a(0) =3a(1) =0a(2) =6a(3) =3a(4) =0a(5) =6a(6) =6a(7) =0a(8) =18a(9) =0a(10) =0a(11) =6a(12) =6a(13) =0a(14) =24a(15) =3a(16) =0a(17) =6a(18) =12a(19) =0a(20) =24a(21) =6a(22) =0a(23) =6a(24) =15a(25) =0a(26) =18a(27) =6a(28) =0a(29) =12