Theta series of lattice with Gram matrix [2 1; 1 3].

Terms

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