Theta series of D_21 lattice.

Terms

a(0) =1a(1) =840a(2) =95802a(3) =3504816a(4) =55350120a(5) =465944304a(6) =2610853840a(7) =11337146784a(8) =40208417466a(9) =123411903160a(10) =335056780464a(11) =830096613360