Theta series of direct sum of 6 copies of hexagonal lattice.

Terms

a(0) =1a(1) =36a(2) =540a(3) =4356a(4) =20556a(5) =60696a(6) =137916a(7) =325152a(8) =658476a(9) =1023012a(10) =1999080a(11) =3112560a(12) =4446828a(13) =7207992a(14) =10755936a(15) =13150296a(16) =20963052a(17) =27538056a(18) =33706908a(19) =47989008a(20) =64050696a(21) =70696224a(22) =103079952a(23) =124752096a(24) =142308684a(25) =189312156a(26) =237450312a(27) =248276484a(28) =344385504a(29) =397677816