Number of n-dimensional unimodular lattices (or quadratic forms).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =1a(8) =2a(9) =2a(10) =2a(11) =2a(12) =3a(13) =3a(14) =4a(15) =5a(16) =8a(17) =9a(18) =13a(19) =16a(20) =28a(21) =40a(22) =68a(23) =117a(24) =297a(25) =665a(26) =2566a(27) =17059a(28) =374062