Theta series of planar hexagonal lattice (A2) with respect to edge.

Terms

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