It is found that the number, M n , of irreducible multiple zeta values (MZVs) of weight n, is generated by 1 − x 2 − x 3 = n (1 − x n ) Mn . For 9 ≥ n ≥ 3, M n enumerates positive knots with n crossings. Positive knots to which field theory assigns knot-numbers that are not MZVs first appear at 10 crossings. We identify all the positive knots, up to 15 crossings, that are in correspondence with irreducible MZVs, by virtue of the connection between knots and numbers realized by Feynman diagrams with up to 9 loops. * ) Work supported in part by grant CHRX-CT94-0579, from HUCAM.