Theta series of hexagonal close-packing with respect to center of triangle between two layers.

Terms

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